MINERALOGY.
Mineralogy. MINERALOGY is that department of Natural History which makes us acquainted with all the properties and relations of minerals. It is divided into two grand branches, viz. Mineralogy, properly so called, and Geology. Mineralogy treats of the properties and relations of Simple Minerals; while Geology considers the various properties and relations of the Earth, Atmosphere, the Waters of the Globe, and the Mountain Rocks, or those mineral masses of which the crust of the earth is principally composed, and which are generally of a compound nature.
I. MINERALOGY.
1. System of Arrangement.
The arrangement of simple minerals has always been a subject of controversy with mineralogists; and the discussions to which it has given rise have materially contributed to the advancement of our knowledge of the natural and chemical history of minerals. Many, as Berzelius and others, contend for the Chemical arrangement, according to which the species are grouped in conformity with their chemical composition and characters; others, as Werner, Hoffman, &c. reject the pure chemical, and adopt the Mixed Method, in which the species are arranged and determined according to the conjoined external and chemical characters; and of late years the Natural History plan, or the arrangement according to external characters alone, has been advocated by Mohs, Jameson, &c. We are inclined to recommend the latter; and of all the natural history arrangements, we consider that of Professor Mohs as the most philosophical, and we have accordingly adopted it in the present article.
2. Characters of Minerals.
As the characters employed in the natural history system of mineralogy are principally those named external, we shall here confine our attention to these, referring for an account of the others to the article MINERALOGY, already published in the Encyclopædia Britannica. We shall first give an account of the characters used in the construction of the different principal divisions of the system; and next enumerate and define those characters which are employed in the description of the species, subspecies, kinds, and varieties of simple minerals.
I. CHARACTERS EMPLOYED IN THE DETERMINATION OF THE CLASSES, ORDERS, GENERA, AND SPECIES.
I. Regular Form.—II. Cleavage.—III. Hardness.
IV. Specific Gravity.*
I. REGULAR FORM.
1. Simple and Compound Forms.
The first step Crystallography takes in the consideration of the regular forms occurring in the mineral kingdom, is to distinguish them into simple and compound ones. A simple form is contained under homologous planes, or such as are equal, similar, and equally disposed in respect to each other; a compound one is contained under planes, not homologous, or such as are not equal, similar, and equally disposed to each other.
2. Combinations.
A compound form is termed a combination. The combinations consist of the simple forms, and each face occurring in them, belongs to a particular simple form, in as far as it is not homologous with others.
3. Edges of Combination.
The edges, in which the faces of different forms meet or intersect each other, are called edges of combination. The denomination of the edges between the homologous faces depends upon the simple forms themselves, or upon their peculiar situation, and their other qualities.
4. Development of the Combinations.
An object of the greatest importance for crystallography is the illustration of the development of the combinations. A combination is developed by showing of what simple forms it consists, and in what relations those simple forms are to each other. The manner in which this is done is as follows: First, the connection existing among certain simple forms is exhibited; and these simple forms are arranged accordingly into series, the members of which, between certain limits, follow constant laws, and are known in all their geometrical relations, if it is possible to determine their distance from a known member, or to assign them their relative position in a series, which contains the same member. The position of a member in the series is determined by considering the situation of the edges of combination; and the development of the latter will, therefore, depend upon two points; first, to make out the kind of the simple forms they contain; and then, from the observed situation of the edges of combination, to determine to which member of the afore-mentioned series they belong, or which places they occupy in this series.
5. Preparation for the Development of the Combinations.
Let fig. 1, Plate XCVIII., be a combination of two
* Certain varieties of colour, the lustre, and also the streak, are occasionally used in forming the characters of the systematic divisions.
Mineralogy-rhomboids. The faces ADEED, ADE'E'D, ... belong to one, the faces DEE'E'E', ... to the other. Let the edges of combination DE, DE', ... be parallel, and the faces of the two forms that meet in them equally inclined to each other. The plane angles at the apex, or at the solid angle formed by three equal plane angles of the former, are smaller than the same of the latter; and likewise the inclination of the terminal edges, or at those which terminate in the apex, or in the terminal point of the axis AX of the former, is smaller than the same of the latter, which, therefore, is called the more obtuse, whilst the former bears the denomination of the more acute rhomboid. It would not be sufficiently intelligible to derive the relation which exists between the two rhomboids, from the figure in its present state, the absolute dimensions remaining unaltered. Let, therefore, the axis of the more obtuse rhomboid increase, till it equals that of the more acute one, without any alteration in the angles, and consequently in the parallelism of the edges of combination depending upon them. Whilst the axis increases, that part of the faces of the more obtuse rhomboid, which is visible in the combination, will become narrower and narrower, till it disappears, when the length of the axis is equal in both the forms. The planes of the more obtuse rhomboid are in this case tangent to the terminal edges of the more acute one; and the absolute dimensions are now in that state, in which they allow of a clear development of the relations between the forms which the combination contains.
6. Upright Position and Horizontal Projection.
Place a rhomboid in such a position that its axis is vertical. This is called the upright position. From the six angles of the rhomboid, B', C', ..., fig. 2, which are no apices, draw perpendicular lines B'O', C'R' ... to a horizontal plane, and join the points in which these perpendiculars meet with the plane, by straight lines O'R', R'Z' ... The regular hexagon H'O'R'Z'N'T' produced by those lines is called the horizontal projection of the rhomboid.
7. Relation of the Two Rhomboids expressed by the Side of the Horizontal Projection.
By comparing the planes of the horizontal projections HORIZNT and H'O'R'Z'N'T' belonging to the rhomboids, we find that, the axes being supposed equal, the horizontal projection of the more obtuse is four times as large as that of the more acute; or it is to the same in the ratio of 4:1. From this follows the ratio of their sides = 2:1. Therefore, two rhomboids, the horizontal projections of which are in the ratio of 4:1, or the sides of these in that of 2:1, the axes being supposed equal, will be able to produce a combination in which the edges of combination are parallel to each other; also to the terminal edges of the more acute, and to the inclined diagonals (those which join the apex with the opposite angle of the faces) of the more obtuse rhomboids; provided the absolute dimensions allow the space to be limited by both the forms at the same time. This is one of the relations between simple forms, which are useful and necessary for explaining
the combinations, and of which the other relation Mineralogy will be explained in the following paragraphs.
8. Fundamental Form, Derivation, Derived Form.
What has been said above leads to a general method, one form being given or chosen, to find one or several others, which are in such relations to it, as to be fit for explaining the combinations. The form chosen for this purpose is called the fundamental form or type; the proceeding by which the other forms are produced the derivation, and those forms themselves the derived forms.
9. Relation of the Two Rhomboids expressed by the Axis.
The easiest method of expressing the relation of the derived rhomboids to the fundamental form (§ 7.) is not that by the sides of the horizontal projections, the axes being supposed equal. Let, therefore, the derived rhomboid, without any alteration in its angles, diminish in size (as could be done by sections parallel to its faces) till its horizontal projection becomes equal to the horizontal projection of the fundamental form; its axis will decrease to half of its former length. Now, the horizontal projections being supposed equal, the axis of the derived rhomboid will be to the axis of the fundamental form in the ratio of , an expression of the relation between the two forms, which, on account of its easy application, we shall retain and make use of as we proceed.
10. Inversion of the Proceeding.
The mode of proceeding, by which the more obtuse rhomboid has been derived from the more acute one, can easily be inverted; setting out from the more obtuse one, we can, by the same way, in an opposite direction, derive the more acute rhomboid. The diagonals being drawn upon the faces of the rhomboid, and by planes laid through three and three of them, those parts which are situated on their outside being taken away, what remains will be a rhomboid more acute than the fundamental form. The axes of both these forms are equal, whilst the sides of the horizontal projections in the fundamental and the derived rhomboid are in the ratio of 1:1. Now, the horizontal projections being equal, the ratio of the axes will be = 1:2.
11. Generality of the Relations.—Series.
These modes of proceeding, and the relations between the derived forms, are general. If, therefore, from one rhomboid, taken for the fundamental form, another more obtuse has been derived; this same more obtuse rhomboid, considered as a fundamental form, will yield another still more obtuse; and if, on the other hand, from the fundamental form a more acute rhomboid has been derived, the same proceeding applied to the resultant form will give another still more acute; and this may be continued on either side ad infinitum. The ratio between the axes of any two subsequent rhomboids, the horizontal projections being supposed equal, has everywhere the same exponent. The axes are therefore in a geometrical progression, and the rhomboids repre-
Mineralogy. sented by these axes are themselves said to form such a progression or a series.
12. Laws of Progression of the Series.
Let A be the fundamental form, its axis = . Let B represent the first, C the second more obtuse; B' the first, C' the second more acute rhomboid, the rhomboids will follow each other thus:
their axes will be
or they are in the ratios of
equal to those of the powers of the number 2.
The more obtuse rhomboids B, C... and the more acute ones, B', C'... derived from a given or supposed fundamental form A, their horizontal projections being equal, produce a series, in which the axes of the subsequent members increase on one side, and decrease on the other, like the powers of the number 2.
13. Designation.
The method of designating crystallizations, whether simple or compound, is founded on the present and similar series, to be developed afterwards. Represent the fundamental form by any arbitrary letter, in this case, according to the practice hitherto observed, by R. The sign of any other member of the series contains the same letter; the exponent of the fundamental number of the series, which, in the present case, is the number 2, being added for the sake of expressing the place occupied in the series by the number to be designated. This yields the crystallographic sign for one member, and by applying the same proceeding to the others, the designation also of the whole series.
14. Continuation.
The above mentioned part of the series of rhomboids is
the ratio of their axes
its designation, therefore,
and in the same way , the general term for each member of the series, which may be transformed into a particular one, by putting whole numbers, positive or negative, instead of in the expression.
15. Usefulness of the Designation.
From the ratio of the axis to the side of the horizontal projection being known in a rhomboid, all the rest of its ratios, its dimensions (plain and solid angled), &c. can be deduced. The side of the horizontal projection is supposed equal in all the members of the series, and made = 1 in the calculations
which refer to the rhomboid. The designation contains therefore, by representing the relation of the axes, every thing required as a basis of calculation; and since it does not require any figures (for instance those of a fundamental form), the letter R signifying by itself a rhomboid, the designation is also evident, and upon this depends the easiness of its application in crystallography.
16. Limits of the Series.
There can be no doubt of being able to obtain any possible value; or, which is the same, the series may be continued as far as we choose. This produces always new rhomboids, as long as has a finite value. On one side the axes will increase, if increase and remain positive; on the other the axes will decrease, if the negative value of increases. Let become infinite, the axis will likewise be infinite; let become infinite, the axis will be infinitely small. It is clear that the limits of the series will be, on one side a rhomboid of an infinitely large axis, on the other a rhomboid of an infinitely small axis, and their several signs must therefore be and ; so that
represent the series between its limits.
17. The Limits are Regular Six-sided Prisms.
It is very easily shown that a rhomboid of an infinite axis is a regular six-sided prism; for at the same time, as the axis increases, the six faces of the rhomboid approach nearer and nearer to parallelism with the axis, and they become really parallel with it, if the axis becomes infinitely long. For rendering more evident in what manner the regular six-sided prism is the limit of the series of rhomboids, we can imagine each face of the rhomboid to make a revolution round an immoveable line QS, fig. 3. This line is the side of that regular hexagon, which can be inscribed into the horizontal projection HORIZNT; the hexagon itself will be the basis or transverse section of the prism, and it differs from the horizontal projection by both its contents and its situation. If the axis of the rhomboid decrease till it ultimately evanesce, the faces contiguous not only to one, but also those contiguous to the other apex, coincide in one plane; and the rhomboid is changed into a plane figure, equal and similar to the horizontal projection, to which it is parallel, and appears, therefore, in all the combinations as a face perpendicular to the axis. It must here be remarked, that forms of infinite dimensions cannot be produced by themselves, or as simple forms, but appear only in combinations.
18. Position.
The series of rhomboids, already described, contains every thing concerning the dimensions and the ratios of its members, as far as each of them is considered singly or by itself. But there is still one object of great importance to be noticed, if those members are considered connected together, or in combinations. This is their position. It is evident that two subsequent members of the series, as, for instance, R and R+1, or, in general terms, R+n and R+n+1, will produce the above combination
Mineralogy. in which the edges of combination are parallel, not only with each other, but also with the terminal edges of the more acute, and with the inclined diagonals of the more obtuse rhomboids; but they will produce this combination only in the case of their being in such a position, that the terminal edges of the one are in the same plane with the inclined diagonals of the other, which plane passes at the same time through the axis, as is shown by fig. 2, Plate XCVIII. This position of two rhomboids is termed the turned position, because it arises when a rhomboid is turned out of its former position, under an angle of or . If a rhomboid, in the turned position, undergo a new revolution of or , it returns to that which it occupied before, and this is called the parallel position. Rhomboids that affect a parallel position with each other, have their terminal edges and their inclined diagonals distributed in such a manner, that the terminal edges of both, on one side, and the inclined diagonals of both, on the other, fall into one and the same plane, passing through the axis.
19. Position of the Members in respect to each other.
The position of the fundamental form R is considered as the normal position, to which those of the derived members are referred. In reference to R, and will be in a turned, and in a parallel, and in a turned position again, and so on; from which it follows, that any two subsequent, or, in general, any two members of the series, between which an even number of members (0 in the above case being considered as even) are wanting, will be in the turned position, whilst any two members of the series, between which an odd number of members are wanting, will affect the parallel position. All those members, therefore, which have their exponent an even number, are in the parallel, those which have their exponent an odd number, in the turned position, if compared with R, the fundamental form of the series. The position exercises no influence upon the regular six-sided prism, since, by turning it under angles of and , its faces will come into their former situation.
20. Scalene Six-sided Pyramids.
The rhomboid allows several forms to be derived from it, which are not themselves rhomboids like the original. Lengthen the axis of a rhomboid, fig. 4, Plate XCVIII, on both sides to an indefinite but equal distance, and from the angles B, C, ... draw straight lines to the terminal points A', X', of the lengthened axis. The planes which can be laid through any two contiguous lines of these, and the lateral edges, BC, CB, ... of the rhomboid will produce a form, which, from its faces being scalene triangles, is called a scalene six-sided pyramid. The solid angles, A', X', at the terminal points of the axis, are its apices; the edges which terminate in these apices are the terminal, and those which correspond with the lateral edges of the rhomboid are the rhomboidal edges of the pyramid. The terminal edges allow of a farther distinction into more obtuse and more acute ones; the faces being on AB, the first, inclined under a greater, on AC, the other, under a less angle.
21. Their Axis a Multiple of the Axis of the Fundamental Form.
Instead of lengthening the axis, we may conceive it to be multiplied by a certain number, expressed in general by . The values of must be determined by observation, or, which is the same, they must be derived from combinations containing six-sided pyramids. They cannot, therefore, be fixed arbitrarily, if we expect them to be confirmed by observation.
22. Series of Scalene Six-sided Pyramids.
From each rhomboid, several scalene six-sided pyramids may be derived, and we are authorized to expect as many forms of this kind as observation has discovered different values for . By deriving scalene six-sided pyramids, according to a constant , from the subsequent members of the series of rhomboids, a series of such pyramids is produced, the axes of which partake of the law followed by those of the series of rhomboids. For the horizontal projections of the pyramids are identical with those of the rhomboids, because the rhomboidal edges of the pyramids have the same situation as the lateral edges of the rhomboids from which they are derived; and the axes of the pyramids, being equal to the axes of the rhomboids, multiplied by a constant number , will therefore persist in the ratio of those.
23. Designation.
The letter P, in general, signifies a pyramid, but more particularly a six-sided pyramid, if referred to a form derivable from the rhomboid. The quality of a scalene six-sided pyramid, in which there occur differences according to the relation of its axis to that of the rhomboid, must be made evident by the designation. Include the general sign for the pyramid, expressed in such a manner as to refer to the rhomboid from which it is derived, within crochets ( ), and add the number of derivation, or that by which the axis of the rhomboid has been multiplied, in order to produce the axis of the pyramid, in the form of an exponent; the result will be the crystallographic sign of a scalene six-sided pyramid. Thus represents a scalene six-sided pyramid derived from R+1 by multiplying its axis by the number 3; and is the general term of any or of each series of scalene six-sided pyramids, which can be derived from a series of rhomboids having R for its fundamental form, according to the value of , determined for each particular series. If the axis of the rhomboid from which a scalene six-sided pyramid is derived, and the number of derivation are known, the dimensions of the pyramid are easily to be found; thus every thing that has been said above (§ 15.) in respect to the designation, can be equally applied in the present case.
24. Values of .
Although the value of be, as far as experience goes, most commonly = 2, 3, or 5, yet it sometimes affects others, and even fractionary numbers. The only thing to be said in general of the value of is, that it must be greater than 1, rational and positive.
Every series leads to its limits; it is, therefore, to be expected, that the series of scalene six-sided pyramids will have limits of their own. It appears by an easy geometrical construction, that scalene six-sided pyramids, derived according to a constant , from the different members of a series of rhomboids, or even from any rhomboid though it be no member of that series, if cut perpendicularly upon, and through the centre of their axes; that such pyramids will have a common, or equal and similar transverse section, provided only the horizontal projections of these rhomboids have been equal. This section is an equilateral dodecagon of alternately equal angles. The limits of a series of scalene six-sided pyramids must therefore be a scalene six-sided pyramid of an infinite axis; which, since cannot become infinite, must be derivable from a rhomboid of an infinite axis, that is to say, from a regular six-sided prism. The limit will, therefore, appear in the shape of an unequiangular twelve-sided prism, of the same transverse section, which the finite members of the series produce. Each series of scalene six-sided pyramids is limited by a prism of this kind; the number of different prisms will therefore be equal to the values of , upon which the angles of their transverse sections depend. The opposite limit, viz. the scalene six-sided pyramid of an infinitely small axis again appears in a plane figure, equal and similar to the horizontal projection, its faces being perpendicular to the axis of those forms with which it is combined. The general sign of an unequiangular twelve-sided prism is . The face perpendicular to the axis does not require any particular designation, since that of (§ 15) is already applied to it. Respecting the position, both of the scalene six-sided pyramids, and of their limits, the unequiangular twelve-sided prisms to each other, and to the rhomboidal form from which they are derived; §§ 18 and 19 contain the necessary explanations.
26. Subordinate Series of Rhomboids.
There are several rhomboids in connection with , without being members of the series derived from it, because their axes, the horizontal projections being equal, are not products of the axis of , multiplied by powers of the number 2. These rhomboids follow, however, the law (§ 12) which governs the series of rhomboids immediately derived from , and their axes are results of the axes of the members of this series multiplied by a certain coefficient. Series arising in this way are termed subordinate series, whilst that which has been derived from has the relative name of the principal series.
27. Coefficients of the Subordinate Series, and how the Members of these belong to each other and to the Members of the Principal Series.
Members of the subordinate series are geometrically obtained by laying planes into the homologous terminal edges of the scalene six-sided pyramids derived from the members of the principal series, and by enlarging these planes till they inclose the
space by themselves. By applying the planes to the more obtuse terminal edges, the resulting coefficient
is ; by applying them to the more acute
ones, it follows . If the three most com-
mon values of are one after the other put into the expressions, each of the two coefficients give rise to members of two different subordinate series; but at the same time it yields one member of the principal series, namely, if becomes equal to a power of the number 2. These numbers of the principal series are not, however, objects of the present consideration. The subordinate series, whose coefficient contains, besides a power of the number 2, the number 5, is styled the first; that whose coefficient, also besides a power of the number 2, contains the number 7, the second subordinate series. The members of the subordinate series arrange themselves with those of the principal series in such a manner, that the axes of those which are put together stand in the ratio of . According to this disposition, a rhomboid, whose axis contains five-fourths of the axis of , or which is , its horizontal projection being equal to that of , is of the first subordinate series, and its designation ; a rhomboid whose axis is , is of the second subordinate series, and its designation . Any other value of affords other subordinate series. The members of a subordinate series cannot be interpolated, or put between those of the principal one, without undoing both these series themselves. The limits of the subordinate series are identical with those of the principal series; the position of their members follows from their derivation.
28. Isosceles Six-sided Pyramids.
Apply pairs of planes to the terminal edges , of a rhomboid, fig. 5, Plate XCVIII., in such a manner and inclination, that those from the upper apex, and , may intersect those from the under apex, and , in a plane figure , similar to and parallel with the horizontal projection. The result will be an isosceles six-sided pyramid. The axes of both the pyramid and the rhomboid being equal, as appears from the derivation, the sides of their horizontal projections are in the ratio of 3:2. Hence the horizontal projections being supposed equal, the ratio between the axis of the pyramid and that of the rhomboid will follow , or the first will contain of the axis of that rhomboid from which it is derived. The isosceles six-sided pyramid, derived from , is designated only by (§ 23), on account of its being always obtained by a similar proceeding from its rhomboid.
29. Series of Isosceles Six-sided Pyramids.
Each member of the principal series of rhomboids has its concomitant isosceles six-sided pyramid of the ratio just stated, the horizontal projections being equal. This gives rise to a series of isosceles six-sided pyramids, the axes of which, their horizon-
Mineralogy. tal projections being equal, increase and decrease as the powers of the number 2; that is to say, they follow the general law of all those forms which are derived from the rhomboid.
30. Limits and Position.
The limits of this series are regular six-sided prisms of infinite axes, like those of the series of rhomboids. Let the axis of an isosceles six-sided pyramid increase, whilst the horizontal projection remains unchanged, the inclination of the faces at the edges of the basis (those in which the faces from different apices meet) will likewise increase till it becomes , in which case the axis will be infinite. In this case, each two corresponding faces from the different apices coincide into a single plane parallel with the axis, and the isosceles six-sided pyramid is thus transformed into a regular six-sided prism, the basis or transverse section of which is the horizontal projection itself. By this basis and its situation the present prism differs from that (§ 17), which limits the series of rhomboids; and by this the necessity of considering them as two distinct forms becomes evident. The crystallographic sign for the limit of the series of isosceles six-sided pyramids is . The opposite limit, merely a face perpendicular to the axis of any of the foregoing forms, requires no particular designation. Since the faces of an isosceles six-sided pyramid, when this is turned round under or , resume their former situation, there is no difference prevailing in the position of the members and limits of this series, either in respect to themselves, or to the other forms derived from the rhomboid.
31. Derivation from the Isosceles Four-sided Pyramid.
Consider an isosceles four-sided pyramid (Plate XCVIII. fig. 6), a form contained under eight equal and similar isosceles triangles, as a fundamental form; place it in its upright position, by making its axis vertical, and apply to it the process § 5. The tangent planes will limit a space representing again an isosceles four-sided pyramid, the plane angles of which at the apex, and the inclination of the faces at the terminal edges, will be greater than the same in the fundamental form, and hence it will likewise be the more obtuse of both.
32. Ratio of the Derived Pyramid to the Fundamental Form.
The axes of these pyramids are equal to each other. The horizontal projection of the more obtuse is that square which can be circumscribed to the horizontal projection of the fundamental form; and, accordingly, its content twice the content of the horizontal projection of the fundamental form, the ratio of their sides . Suppose now the horizontal projections of the two pyramids to be equal, the axis of the derived more obtuse pyramid will be to the axis of the fundamental form in the ratio of
33. Inversion of the Proceeding.
This proceeding can be applied inversely, in order to obtain from the fundamental form the same more acute four-sided pyramid, from which, by the proceeding applied directly, the fundamental form would have been the result. This inverse application is as follows: Draw in the faces of the fundamental form perpendicular lines from the apices to the edges at the basis, lay cutting planes through every two contiguous of these lines, and separate those parts of the pyramids which lie outside of them. The remainder, inclosed by the cutting planes, will be again an isosceles four-sided pyramid, having the same axis as the fundamental form, but a horizontal projection, whose content is half the content of the horizontal projection of the fundamental form, and the ratio of their sides, therefore, . The horizontal projections being made equal, the axis of the derived more acute pyramid is to the axis of the fundamental form in the ratio of , which is the inverse of the ratio deduced above.
34. Series and Designation.
By continuing the derivation, the more obtuse pyramid produces another still more obtuse; the more acute another still more acute, and thus arises a series of isosceles four-sided pyramids, whose axes, their horizontal projections being equal, increase and decrease as the powers of the square root of 2;
which law of progression can be expressed by , or . The designation of this series is concordant with the principles already laid down and followed (§ 13). The fundamental form receives the letter . Hence its neighbouring members will be
their axes, that of being ,
their ratio to each other,
and the general term of the series, which, by the substitution of any whole positive or negative number in the place of , gives a certain determined member. The present designation is quite the same as that in § 28, and as another to be mentioned in § 44. However, the observation in page 431 is sufficient to show the impossibility of any confusion or ambiguity that could arise from making use of identical signs for the expression of different forms.
35. Limits.
If becomes greater or smaller than any given number, a transformation takes place similar to that by which the isosceles six-sided pyramid gave rise to the regular six-sided prism: the series of isosceles four-sided pyramids terminates on one side in an unlimited four-sided prism, on the other in a plane figure, equal, similar, and parallel to the horizontal projection, and these two forms represent the limits of the series. In respect to the first, however, there
Mineralogy. occurs the particular circumstance, that the series is doubly limited; because the different members in their succession assume a different position. The derivation shows the pyramids, and , to stand in such a position towards , that the sides of their bases are parallel with the diagonals of the basis of ; whilst, in and , the sides and the diagonals are parallel with the same lines in the basis of the fundamental form. The former are said to be in a diagonal, the latter in a parallel position with ; and every thing contained in § 18 and § 19, in respect to position, may be applied here, if only, instead of and , a revolution of is imagined. Suppose now the two different prisms, the regular six-sided, as well as the rectangular four-sided, in both their peculiar positions. The faces of the first will, after having been duly turned, assume their former situation, which is not the case in the second; and hence it becomes necessary to adopt two rectangular four-sided prisms of an infinite axis as limits of the series of isosceles four-sided pyramids, one being in a parallel, the other in a diagonal position with . The sign of the first is , that of the second . The opposite limit, where there is no difference in the position, is represented by ; and the whole series of isosceles four-sided pyramids between its limits appears thus,
36. Scalene Eight-sided Pyramids.
With the isosceles four-sided pyramids there are connected scalene eight-sided pyramids, contained under sixteen equal and similar scalene triangles (Plate XCVIII. fig. 7). These eight-sided pyramids depend upon the four-sided by the same process of derivation, by which the scalene six-sided pyramids take their rise from the rhomboid. The application of this process to the isosceles four-sided pyramid supposes, however, a preparation of this form, which is effected by enlarging its faces beyond the edges at its basis, and by drawing in these enlargements triangles, equal and similar to the faces of the pyramid. Thus, the points are fixed in two squares that are perpendicular to the axis , in its terminal points, or in the apices of the pyramids. Now, produce the axis of the pyramid on both sides to an indefinite but equal length, or multiply it by a number , greater than 1 positive and rational (§ 24). Join, then, the upper terminal point of the lengthened axis with the points in the under, the under terminal point with the points in the upper square, by straight lines. The points , in which these lines intersect each other, will lie in the prolongation of the basis of the four-sided pyramid. We now join these points with the neighbouring angles of the base by straight lines, the result of which will represent the basis of the derived scalene eight-sided pyramid, which may now be completed without difficulty. The most common, though not the only values given for by nature, are 3, 4, and 5.
37. Series of Scalene Eight-sided Pyramids.
If the number of derivation be constant, the re-
sultant scalene eight-sided pyramids have similar bases, the axes of the isosceles four-sided pyramids may be whatever they will. The application of the described proceeding to the subsequent members of the series of isosceles four-sided pyramids will, therefore, remaining for all the members the same, not only produce a series of scalene eight-sided pyramids, subject to the law followed by the isosceles four-sided pyramids, which is that of ; but the bases or transverse sections of all the members of this series will be similar to each other. The designation of an indeterminate th member of such a series is , and it is evident, that as many values of as experience gives, so many different series of scalene eight-sided pyramids will arise.
38. Limits.
The limits of those series are, on one side unlimited unequiangular eight-sided prisms, the transverse sections of them being similar to the bases of the members of the series; on the other side a plane figure, which in the combinations appears as a face perpendicular to the axis. This is evident from what has been said above, and there remains only to be added, that the prisms of an infinite axis, coming into consideration in two different positions, they must be taken for two different forms, or as double limits of the series. These two positions are the parallel and the diagonal, as in § 35; the parallel being that which prevails between scalene eight-sided pyramids and that isosceles four-sided from which they are derived; whilst forms of this kind in the diagonal position are supposed to have undergone a horizontal revolution of . Now the eight-sided prisms may be considered as scalene eight-sided pyramids, derived from isosceles four-sided pyramids of an infinite axis, namely, the rectangular four-sided prism, according to a certain value of . The necessity of considering the four-sided prism in two different positions (§ 35) must therefore be extended to the eight-sided. The designation of the series of eight-sided pyramids, between their limits, will accordingly be thus:
39. Subordinate Series.
There are series of isosceles four-sided pyramids, belonging to that of § 33, which, in reference to the latter, or the principal series, are termed subordinate series. The members of these series are obtained by placing tangent planes in the homologous terminal edges of the scalene eight-sided pyramids; the same proceeding which applied to the scalene six-sided pyramids produced the subordinate series of rhomboids. The coefficient for the more obtuse terminal edge
(if ) is ; that for the more acute
one (under the same supposition) . If be determined, each of those coefficients gives a mem-
Mineralogy. ber of a particular series. The members of the principal and of the two subordinate series arising from
and are said to belong together in this order. An isosceles four-sided pyramid, therefore, whose axis, the horizontal projection being equal to that of , is
first subordinate series, and bears the designation of ; and a similar pyramid, the other circum-
stances remaining the same, with an axis
is the member of the second subordinate series, expressed by the designation . The limits of
the present series coincide with those of the principal series. The positions of its members in respect to each other, and to the members of the principal series, will become evident, by comparing what has been stated of their derivation with § 27. regarding the position of the subordinate series of rhombohoids.
40. Scalene Four-sided Pyramids.
If in the basis of an isosceles four-sided pyramid, the diagonals are supposed unequal, the pyramid itself is transformed into a scalene four-sided pyramid, or into one whose basis is a rhomb, its faces scalene triangles, and its terminal edges of a different magnitude, the one more obtuse the other more acute, as is represented by ABOBCX, fig. 8. From this we may conjecture that several of the preceding methods of derivation, though with some modifications, will also in this case be applicable.
41. Derivations from it. Auxiliary Form.
Apply to the homologous terminal edges of a scalene four-sided pyramid tangent planes, and enlarge them till they intersect each other in every possible direction; the result will be no form limited on every side, or such as is finite in all its dimensions. If the tangent planes are laid in all the terminal edges of the fundamental form, a form limited from every side will indeed appear, but this form is not a simple one, its faces being homologous only by four and four (§ 1). The form thus arising represents a four-sided pyramid, with an oblong rectangular basis, AFGHIX, fig. 8; and most of the crystallographers consider it as such, and term it accordingly. In this place it must be considered only as an auxiliary or intermediate form, which is not the derived form itself, but useful and auxiliary for its derivation.
42. Derived Form.
Suppose tangent planes to be laid in the terminal edges of the auxiliary form, in such an inclination that those from the upper apex produce by their intersection with those from the under apex a rhomb similar and parallel to the basis of the fundamental
form, and situated in the prolongation of this basis. Mineralogy. The result will be a scalene four-sided pyramid, the basis of which is similar to that of the fundamental form; but the plane angles at the apex, and the inclination at the terminal edges, being greater than in this form, the derived will be more obtuse than the fundamental form.
43. Ratio to the Fundamental Form.
The two pyramids, as produced by the derivation, have the same axis, the ratio between the basis of the derived, and the basis of the fundamental pyramid being that of . This ratio is evident, since the basis of the auxiliary form is double of the basis of the fundamental form, and that of the derived form again double of the basis of the auxiliary form. Hence the horizontal projection of the two forms being supposed equal, the ratio between the axes of the derived and of the fundamental pyramid is that of . The process of derivation, by which the more obtuse pyramid is produced, is liable to an inversion like that in § 10.
44. Series. Designation. Limits. Position.
From a continued derivation on both sides of the fundamental form, a series of scalene four-sided pyramids, of equal and similar bases, will evidently arise, the axes of which increase on one side and decrease on the other, like the powers of the number 2. will be the sign of an indeterminate th member of the series, and if becomes infinite, the series reaches its limits, which are on one side an obliquangular four-sided prism, whose transverse section on the other side is a horizontal plane, whose figure is equal and similar to the horizontal projection of the fundamental form. The designation of the series between its limits becomes thus:
It must be remarked, that such differences on account of the position of the members of the series as are met with in the rhomboid (§ 18) and the isosceles four-sided pyramid (§ 35), are not to be found in the scalene four-sided pyramid.
45. Further Derivations.
The members of the present series are, or this series itself is, now the foundation of several other derivations; and although the forms derived by them will be nothing but scalene four-sided pyramids and obliquangular four-sided prisms, yet the variety in the relations of those forms is great enough to surpass that of the forms in connection with the rhomboid, and with the isosceles four-sided pyramid, for which reason it is one of the most interesting objects of crystallography. The derivations already mentioned apply as well to the fundamental form itself as to the auxiliary form; and they are similar to that which has been employed in deriving the scalene eight-sided from the isosceles four-sided pyramid.
46. From the Fundamental Form.
Instead of the isosceles (§ 37), suppose the scalene
Mineralogy. four-sided pyramid to be the fundamental form, and prepare it for derivation by enlarging its planes beyond the edges at the basis, and by drawing triangles equal and similar to the faces of the pyramid in these enlargements. The points will no longer be the angles of squares, but of oblong rectangles, the planes of which are perpendicular to the axis AX in its terminal points. Produce now the axis of the scalene four-sided pyramid on both sides to an indefinite, but equal length, or, what comes to the same, multiply it by a number , enjoying the general properties mentioned, §§ 24, 26. Draw straight lines from the points in the lower rectangle to the upper apex , from the points in the upper rectangle to the under apex of the lengthened axis, and join their intersections in the plane of the enlarged basis by straight lines with the angles of this basis. The resultant octagon will not have alternately equal angles, like that in § 36, which is the basis of the scalene eight-sided pyramids, but it will be irregular, fig. 9, since of the angles , only the opposite are equal to each other. A form constructed upon such a basis cannot be contained under equal and similar planes, or it cannot be a simple form. Like the four-sided pyramid of an oblong rectangular basis, it is considered as an auxiliary or intermediate form, whose resolution gives the simple forms of which it consists.
47. Resolution of the Auxiliary Form.
This resolution is executed by enlarging those places which are equal and similar to each other, till the rest disappear. In the present case, the resolution produces two different scalene four-sided pyramids of equal axes, their bases being different amongst themselves, as well as from the bases of the fundamental form. They are termed scalene four-sided pyramids of dissimilar bases, derived from the fundamental form, and more particularly that in which the long diagonal of the fundamental form remains unaltered, the pyramid belonging to the long: that in which the short diagonal remains unaltered, the pyramid belonging to the short diagonal of the fundamental form.
48. Designation.
This important difference between the two forms must be expressed by the designation. The designation used for the scalene eight-sided pyramids in § 37, if referred to forms in connexion with the scalene four-sided pyramids, denotes at the same time both of the pyramids just mentioned. In order to make it applicable to each of them singly, it is now necessary to express their difference in respect to the diagonals of the fundamental forms, which is effected by adding the signs and . Thus represents a scalene four-sided pyramid of dissimilar basis, derived from according to the number , which belongs to the long diagonal; , another pyramid of the same properties which belongs to the short diagonal of .
49. Ratios.
The pyramids just mentioned differ from the mem-
bers of the series (§ 44), 1st, in their axes, which, the Mineralogy. axis of being , are expressed by ; 2d, by the ratio of the diagonals of their bases. Let in the ratio of the axis to the long and to the short diagonal be that of , or the ratios of the same lines in that of ; the ratio of the homologous lines will be
as follows easily from the consideration of a few triangles in the figures required for explaining the derivation. Hence the ratio between the diagonals of the bases in the derived forms, that of the fundamental form remaining constant, depends only upon the number . Accordingly, if be supposed constant, all the pyramids of this kind, derived from scalene four-sided pyramids of similar bases, will likewise, as far as they belong to one or the other diagonal, contain similar bases or transverse sections, the axes of the forms, subservient to the derivation, may be whatever they will.
50. Double Series.
If those forms are the members of the above series, each gives rise to two series of derived pyramids of a dissimilar basis, viz. one whose members refer to the long, and another whose members refer to the short diagonal of the basis of the fundamental form. From each of those series having constant transverse sections in all their members, it appears that the obliquangular four-sided prisms, limiting them, must likewise be subject to the equality of transverse sections or bases. Both the series stand, therefore, between their limits, thus:
What has been observed in § 44 in respect to position, may be equally applied here. The values of hitherto most commonly, though not exclusively observed, are . But neither in this case are they the only ones.
51. Derivations from the Auxiliary Form, § 41. Ratios of the Series.
Instead of the fundamental form , or of , suppose the auxiliary or intermediate form, belonging to it, to take its place; by applying to it the proceeding described in §§ 46, 47, the form produced is a compound one like that in § 46, but its resolution yields again two simple forms, which are also scalene four-sided pyramids, whose bases are dissimilar to those of the fundamental form. These pyramids can be distinguished from each other by referring, the one to the long, the other to the short diagonal; from those derived in § 47, by the form to which the derivation is applied, since, in § 47, it is the fundamental form itself, in the present case, the auxiliary form belonging to it; which latter circumstance is expressed in the crystallographic sign by the letter
Mineralogy. added to . From the dimensions of the three lines disposed perpendicularly to each other in the pyramid , the axis and both the diagonals, being in the ratio of , it will follow, the ratio of the homologous lines in the scalene four-sided pyramids of dissimilar basis, derived from the auxiliary form, which belongs to the long diagonal of the fundamental form, or in
The dependence of the ratios between the diagonals of the basis, only from , is evident; and this remains unaltered, how much soever and may be allowed to vary. If the derivation is applied to the whole series in § 44, there will arise two series of scalene four-sided pyramids, which proceed according to the law of the fundamental series, and are limited by obliquangular four-sided prisms, partaking of the similarity in the transverse sections of all the members. The crystallographic designation of the series, between their limits, stands thus:
The values of are here the same as in the above mentioned cases. To the position applies what has been said in § 44.
52. Subordinate Series.
That there are certain subordinate series belonging to the series § 44, which, in reference to the former, may also be considered as the principal series, can easily be supposed from the agreement existing between the forms derived from the scalene and those derived from the isosceles four-sided pyramid. In order to obtain the members of these subordinate series, enlarge the faces of the fundamental form, fig. 10, Plate XCVIII., on both sides; draw in the enlarged faces triangles, equal and similar to the faces of the fundamental form; through the point , thus determined, lay rhombs, similar and parallel to the basis of the fundamental form; multiply the axis by a number ; join the points , of the lengthened axis by straight lines with the said points ; and, lastly, reduce the derived pyramid which has a basis similar to that of the fundamental form, to an equal horizontal projection with it. The number being not yet determined, the coefficient of the subordinate series will be ; which, if be equal to any power of the number 2, shows the member to which it belongs to be a member of the principal series. The subordinate series, whose coefficient, besides powers of the number 2, contains the factor 3, is termed the first, and that which, in the same case, contains the factor 5, the second subordinate series. Members of the principal, of the first and of the second subordinate series, which are supposed to belong together, arrange themselves thus: , which numbers
express the ratio between their axes. The designation and the position of the members in the subordinate series is evident from the foregoing. Mineralogy.
53. Resolution of the Auxiliary Form, § 41. Horizontal Prisms.
The only form now left for examination is the auxiliary form, § 41; which, as has been mentioned above, is not a simple one, its faces not being homologous. By enlarging only those planes which, amongst themselves, are equal and similar, there arise two obliquangular four-sided prisms, unlimited in the direction of their axis, and which, therefore, like all the prisms, are forms in which one dimension is infinite. The axes of the two prisms are perpendicular to each other, and have a horizontal position, if the fundamental form be in the upright position. These axes coincide with the diagonals of the basis of the fundamental form produced to an infinite length. Hence the prisms may be considered as scalene four-sided pyramids, one diagonal of which has become infinite; similarly to the vertical prisms, that are scalene four-sided pyramids of an infinite axis. For the sake of distinguishing them from these, they bear the name of horizontal prisms, and their general designation is . More particularly, expresses the horizontal prism in which the longer diagonal, that in which the shorter diagonal of the fundamental form has remained a finite quantity.
54. Series of Horizontal Prisms.
Every scalene four-sided pyramid, whatever its properties may be, has its dependent horizontal prisms. To every series of such forms will, therefore, belong two series of horizontal prisms, to be distinguished by their designation according to the properties of those series. It is, however, remarked, that if we take the common values of , as stated above, the angles of several members of those series, and, therefore, the series themselves, will be identical; and for this reason, one designation will suffice for them. Thus, the number of series of those forms taken together may be reduced to three pairs, of which the first pair belongs to the principal, the others to the subordinate series of scalene four-sided pyramids; each of the diagonals having one series referred to it. The horizontal prisms belonging to a scalene four-sided pyramid are produced, by placing tangent planes in its homologous terminal edges. If those terminal edges connect the terminal point of the axis with the long diagonal, the prism is said to belong, or to be referred, to the long; if they connect it with the short, it is said to belong, or to be referred, to the short diagonal of . The horizontal prisms are remarkable forms, often to be met with in the natural combinations.
55. Limits of the Series of Horizontal Prisms.
By comparing the horizontal prisms belonging to members of a series of scalene four-sided pyramids it becomes evident how, whilst the axis of the pyramid increases, the angle of the horizon-
Mineralogy. tal prism contiguous to the axis of the fundamental form becomes smaller and smaller; whilst the other, at the intersection of the planes from different apices, becomes greater and greater. If the axis of the pyramid become infinite, or the pyramid itself a vertical prism, the first of these angles will disappear, the second become . Hence a horizontal prism is transformed, in this case, in a pair of unlimited parallel planes, perpendicular to the diagonals to which they belong. These planes, which may be considered as forms unlimited, as it were, in two directions, are the limits of the series of horizontal prisms, the axis of the pyramid to which they belong being infinite. The opposite limits, or those which appear, if the pyramid have an infinitely small axis, appear as faces perpendicular to the axis. The series of horizontal prisms between their limits may, accordingly, be represented thus:
For having the designation in every respect complete, the coefficient of the series to which the horizontal prism belongs must be added to the sign for a particular member.
Although this is not a place for entering into the examination of combined forms, yet that peculiar combination which is produced by the two limits of the series of horizontal prisms, and takes the appearance of a vertical rectangular four-sided prism, not yet limited in the direction of its axis, cannot remain unnoticed. This combination is designated by ; it must carefully be distinguished from the rectangular four-sided prisms, limiting the series of isosceles four-sided pyramids, which, abstraction being made of the face perpendicular to the axis, are simple forms; a property not belonging to the rectangular prism in connection with the scalene four-sided pyramid.
56. Derivations from the Hexahedron.
Besides the rhomboid, the isosceles and the scalene four-sided pyramids, there is only one other form existing fit for being considered as a fundamental form, or which, without being derivable from any one of the former, can itself serve as basis to the derivation. This form is the hexahedron, Plate XCIX. fig. 11. There are, in connection with the hexahedron, a great number of other forms, remarkable for their properties, differing, however, from each other more by their general aspect than by their dimensions. The complete assemblage of those forms is obtained in the following way. Bring first the hexahedron in an upright position, so as to bring one of its corners uppermost, and the opposite perpendicularly below it, by which means the rhomboidal axis, passing the two corners, becomes vertical; then consider the possible situations of a moveable plane, tangent to the hexahedron in the uppermost point of the said rhomboidal axis. The different situations the plane can effect are seven in number; but in one of them it becomes parallel to the face of the hexahedron itself. Every one of these situations gives rise to a peculiar form; hence there will exist as many forms as the moveable
plane can assume different situations, and no more. Mineralogy. The forms thus obtained agree in several of their properties, particularly in respect of the kind, number, and situation of their axis, and are as follows: 1. The hexahedron, contained under six squares. 2. The octahedron, fig. 12, contained under eight equilateral triangles. 3. The one-edged tetragonal dodecahedron (fig. 13), contained under twelve rhombs. 4. The hexahedral trigonal-icositetrahedron (fig. 14), contained under twenty-four isosceles triangles, its prominent form being that of the hexahedron. 5. The octahedral trigonal-icositetrahedron (fig. 15), contained under twenty-four isosceles triangles, its prominent form being that of the octahedron. 6. The two-edged tetragonal-icositetrahedron (fig. 16), contained under twenty-four irregular tetragons, in which two of the opposite angles are equal; and 7. The tetracontaocahedron (fig. 17), contained under forty-eight scalene triangles. The dimensions of the three first of these forms are constant, a property not to be met with in the others, of which, therefore, several varieties may be found differing from each other by their angles.
57. Resolution of some of those Forms into Halves.
This assemblage, though it is complete, seems not to contain all the forms in connection with the hexahedron, as they are produced by nature, such as, for instance, the tetrahedron, the pentagonal dodecahedrons, &c. Nevertheless it contains them; for they arise from a particular resolution of some of those mentioned in § 56. This resolution is effected by enlarging half of the number of planes to be met with in the form to be resolved, according to certain rules, and by making the rest of them disappear. The two forms which arise out of the resolution of one of the former are termed halves (not half forms, as the simple four, six, or eight-sided pyramids), and can be easily distinguished by the lesser number of their axis, as some of those that are common to the original forms disappear by the resolution. The two halves are perfectly equal and similar to each other; they differ, however, amongst themselves by that position in which they are placed by the resolution. The position of one of the halves being considered as the direct, that of the other will be the inverse. The latter is changed into the former, by inverting the vertical rhomboidal axis of the form, so as to bring the upper apex lowermost, and vice versa. Thus the halves, produced from octahedron, are the two tetrahedrons (fig. 18, Plate XCIX.), contained under four equilateral triangles; those from the hexahedral trigonal-icositetrahedron, the two hexahedral pentagonal dodecahedrons (fig. 19), contained under twelve irregular pentagons, which have two pairs of equal angles; those from the octahedral trigonal-icositetrahedron, the two-edged tetragonal dodecahedrons (fig. 20), contained under twelve tetragonal faces, in which there is only one pair of equal angles; those from the two-edged tetragonal-icositetrahedron, the two trigonal dodecahedrons (fig. 21), contained under twelve isosceles triangles; and lastly, the halves of the tetracontaocahedron, viz. a, the tetrahedral trigonal-icositetrahedrons (fig. 22), contained under twenty-four scalene
Mineralogy. triangles; b, the three-edged tetragonal-icositetrahedrons (fig. 23), contained under twenty-four irregular tetragonal faces, in which there are not two equal angles; and c, the pentagonal-icositetrahedrons (fig. 24), contained under twenty-four irregular pentagons, whose angles are all different.
58. Resolution of some of the Halves into Fourths.
The three last, or those halves which are obtained from the tetracontaoctahedron, allow of a further dissolution into halves of the halves, or into fourths. These are the tetrahedral pentagonal-dodecahedrons (fig. 25), contained under twelve irregular pentagons, in which there are not two equal angles. The difference between right and left, to be met with in this form, and in the pentagonal-icositetrahedron, deserves some attention. If two-fourths are combined in the same position, which they assume in the resolution, the halves are produced; and if the halves, produced by this combination, are combined likewise in their proper position, they will reproduce the original form, out of which the halves as well as the fourths have been obtained by way of resolution. Most of the original forms and their halves are already known in several varieties of minerals; some of the latter, viz. the tetrahedral pentagonal-dodecahedrons, and the pentagonal-icositetrahedrons, have not yet been found.
59. System of Crystallization and Series of Crystallization.
If only the kind of the fundamental form has been considered, the assemblage of the forms derived from it is called a system of crystallization; but if also notice has been taken of its dimensions, the assemblage of the derived forms receives the denomination of a series of crystallization. These two notions are of the same kind, and differ only by the number of objects they contain, the latter being a particular determination of the former; and both refer not so much to the mere aggregation of forms, as to the relations prevailing amongst them.
60. Denomination of the Systems of Crystallization.
The systems of crystallization, agreeing in number with the fundamental forms, of which there are four, receive their names according to those fundamental forms. That which has been derived from the rhomboid is called the rhomboidal system, because its forms agree with the rhomboid in their general properties; that which has been derived from the isosceles four-sided pyramid, for the same reason, the pyramidal system; that which has been derived from the scalene four-sided pyramid, the prismatic system, on account of the great number and variety of prisms it contains; and that which has been derived from the hexahedron, the tessular system, in order to intimate that there occurs no other system of crystallization in nature which shares in the general properties of the hexahedron. It is evident that any form, if known, will suffice for the determination of the system to which it belongs, even though this form be a limiting one. Only the right rectangular four-sided prism is an exception, since it may be a simple form in the tessular, a double combination
() in the pyramidal, and a triple combination () in the prismatic system. The consideration of the mere form does not decide at all in this case. Some of the means of removing this uncertainty will be explained hereafter.
61. Determination of the Series of Crystallization.
A series of crystallization is determined by any one of its members, which is no limiting form, if the dimensions of it are known. These dimensions, if they are not (like those of the hexahedron, the octahedron, &c.) constant, must be made out by direct measurement. From these the dimensions of any other member, or of the fundamental form, if it has not been measured itself, can be found, in compliance with the relations developed above. The series of crystallization proves of great importance for the determination of the natural history species in the mineral kingdom. It is also an external character of the utmost value in the character of the species. This character requires, therefore, the dimensions of a member of the series to be stated, of which the most eligible is the fundamental form. The limits do not determine the series of crystallization, since, in the rhomboidal and in the pyramidal system, they are common to all; in the prismatic, at least to those series which possess a similar transverse section. Hence the obtaining the limiting forms is not sufficient for the character of the natural history species.
62. General Laws of Combination.
The second advantage flowing from the above inquiries, consists in the accurate understanding of the qualities of combinations, and of the development of their most general laws. The first of these laws stands thus: The forms which nature combines must belong to one series of crystallization. The second, The combination must be effected in that position of the several simple forms it contains, which the derivation assigns to them. Upon these two laws depends the symmetry of the combinations, which, therefore, is not the fundamental law of crystallization.
63. Rhomboidal and Dirhomboidal Combinations.
An accurate investigation of the combinations is one of the most interesting parts of crystallography. Without entering into minute details, some of their relations may be shortly mentioned, as they convey general ideas of the connection between different forms, and as they are, therefore, of consequence in the system of arrangement and discrimination to be explained in this article.
Combinations of the rhomboidal system, produced by simple forms in such a manner that they appear in the combination with the full number of their faces, and in their proper position, are termed rhomboidal combinations. Such are the most common combinations in the rhomboidal system. Suppose, on the contrary, a rhomboid to combine with itself in a turned position, it will affect the shape of a simple form, and appear as an isosceles six-sided pyramid. It is termed a dirhomboid, and designated by . The dirhomboids do not arrange themselves with the isosceles six-sided pyramids in the same se-
Mineralogy. ries (§ 29), because there is a difference existing in the situation of the bases in the one and in the other, as becomes evident in considering the derivation. In a similar way, two equal scalene six-sided pyramids being combined in a turned position, produce a scalene twelve-sided pyramid, which has as little right as the dirhomboid to be ranked with the simple forms, although its faces are all equal and similar to each other. Combinations produced by, or containing forms of this kind, are termed dirhomboidal combinations.
64. Hemi-rhomboidal and Hemi-dirhomboidal Combinations.
It sometimes happens in the rhomboidal system, that the forms enter only with half the number of their faces into a combination. If these combinations contain simple forms, they are said to be hemi-rhomboidal; if they contain any of the above mentioned compound forms under this restriction, they are said to be hemi-dirhomboidal. A further distinction is to be made among such combinations, in as much as the faces contiguous to one apex are either parallel, or inclined to those of the other. The hemi-rhomboidal, or hemi-dirhomboidal, are said, in the first case, to be of parallel, in the other to be of inclined faces. An example will put the importance of this difference in its full light: Enlarge in a scalene six-sided pyramid the alternating faces contiguous to one apex, and, at the same time, those of the opposite apex, which are parallel to the former, the resultant form will take the appearance of a rhomboid, without in reality being a form of this kind. If, on the contrary, the faces enlarged on the opposite apex are inclined to those of the former, the resultant form is contained under six trapezoidal faces.
65. Pyramidal and Hemi-pyramidal Combinations.
A relation similar to that which in the rhomboidal system has been expressed by the name of hemi-rhomboidal, is equally found in the pyramidal system, and here it constitutes the hemi-pyramidal combinations. The hemi-pyramidal combinations of parallel faces refer only to the eight-sided pyramids, which by this affect the shape of isosceles four-sided pyramids, without partaking of their other properties; those of inclined faces refer also to the isosceles four-sided pyramids, which yield forms analogous to the tetrahedron, whilst the result of the scalene eight-sided pyramid is a particular form, contained under eight scalene triangles.
66. Prismatic, Hemi-prismatic, and Tetarto-prismatic Combinations.
The differences already mentioned are particularly remarkable in the prismatic system. From what has been said in respect to the other systems, it becomes evident what is meant by prismatic and by hemi-prismatic combinations. The latter expression refers also to one or to several prisms, whose axes are parallel, if they enter into the combinations with only half the number of their faces. A similar relation of forms in the present system, marked by the expression tetarto-prismatic, arises, when of a scalene four-sided pyramid only the fourth part, as to the
number, of the faces appear in a combination. Such a combination can also be produced by oblique angular four-sided prisms, whose axes are perpendicular to each other, when only half the number of their faces is visible. The hemi and tetarto-prismatic combinations illustrate the oblique, the rectangular as well as the obliquangular prisms produced by nature. These belong altogether to the prismatic system, and none of them is a simple form.
The signs of the hemi-rhomboidal, hemi-pyramidal, and hemi-prismatic, are composed of the signs of the whole forms, and of the number 2, placed below them like a divisor; instead of the latter, the signs of the tetarto-prismatic combinations contain the number 4 as divisor.
67. Tessular and Semi-tessular Combinations.
Those combinations of the tessular system, into which no halves or fourths enter, are called tessular combinations, and in the present place they need no further explanation. Combinations of this system, however, containing halves, are termed semi-tessular combinations. These allow of a further distinction into semi-tessular combinations of parallel faces, and into those of inclined faces, as is the case in the hemi-rhomboidal and hemi-pyramidal combinations. The halves peculiar to the former are those in which every face is parallel to another, as the hexahedral pentagonal-dodecahedron, the three-edged tetragonal-icositetrahedron, and the general aspect of the forms undergoes thereby no alteration. The halves peculiar to the latter have not two faces parallel to each other, as the tetrahedron, the tetrahedral trigonal-icositetrahedron, &c., and the combination itself assumes, or at least approaches to a tetrahedral aspect.
Instead of crystallographic signs, verbal expressions are employed, in the characteristic part of this article, when describing the forms of the tessular system; because the use of the former is in the present system subject to much greater difficulties, without affording services either so beneficial or so numerous as in the other systems.
68. Development of the Combinations.
To develop a combination is to exhibit by itself each of the simple forms which it contains (§ 4). The determination of the kind of these forms has no difficulty whatever. The homologous planes of a combination being enlarged till the rest disappear, one of the forms after the other is produced. To find out their relations, upon the knowledge of which, nevertheless, depends the demonstration of the combinations, is somewhat more circumstantial, and here the series of simple forms, produced by the derivation, show their great utility. The following paragraph contains a general idea of the mode of proceeding followed for this purpose by crystallography, though its full explanation would require too much calculation to be given in this place.
69. Line of Combination, General Formulae for it, and their Application.
Imagine a combination of two simple forms, whose dimensions are known, and which themselves are in
Mineralogy. such a position as is peculiar to the system of crystallization to which they belong. Suppose now two terminal edges, or two diagonals, or one terminal edge and one diagonal, that are situated in a plane which, at the same time, passes through the axis, to be prolonged, till they intersect each other above or below, in a finite or infinite distance from a horizontal plane, laid through the centre of the axis. The straight line measuring the distance between the mutual intersection of the two lengthened lines, and that in which one of the lines meets with the horizontal plane, is termed the line of combination. The length and situation of the line of combination are evidently dependent upon the dimensions of the combined forms; and inversely the situation of the edge of combination (§ 3.) is dependent upon the length and situation of the line of combination: for, join by a straight line the terminal point of the line of combination with one of the points of intersection between the edges and diagonals of the combined forms, amongst themselves or with each other, the prolongation of this line will equally pass through the other point of intersection, and therefore be identical with the edge of combination. Hence if two forms of a system, in a determined position, produce with a third form lines of combination equal both in length and situation, the edges of combination thus produced will be equally situated; and if the two forms enter at once into combination with the third, the edges of combination produced by the first and the third must be parallel to those between the second and the third.
Crystallography develops general formulæ, expressing the quantity of the line of combination respecting the three first systems of crystallization (this not being required for the tessular system), in which due notice is taken of the kind of forms, their position, and the quality of the edges of combination, namely, whether the faces producing them are contiguous to one or to different apices of the simple forms. Of these formulæ, that which answers to the circumstances of a given combination between two known simple forms, is chosen and determined for that particular case, by substituting, instead of the variable quantities, and occurring in them, those finite numbers, which depend upon the place of the members in the series, and those factors by which the axes of the rhomboids and others have been multiplied. Thus the quantity of the line of combination, expressed either by a terminal edge, or by a diagonal, or by the axis of one or the other form contained in the combination, is found. Another formula must now be chosen, answering to a combination between one of these known forms, and another unknown, which produces with it edges of combination parallel to those in the combination of the two known forms. The formula must be determined for the case in question, by the substitution of numbers to and . This can only be done in respect to the known form; and of the unknown remain unaltered in the expression.
Mineralogy. This expression, as is evident from the preceding, must be equal to the value of the line of combination found above. These two equal terms give an equation to be resolved for the values of and .
If the unknown form contains only (as for instance it being a rhomboid, where ), it is determined in the manner already mentioned. If, on the contrary, it contains and at once, another equation must be established in order to determine the second quantity, which is effected in the manner shown already. Some experience in this method of developing the combinations will teach how to take advantage of certain circumstances offering themselves, by which very often it is rendered possible to argue immediately upon one of the unknown quantities or , or even sometimes upon both, and to determine the relations of several forms, according to such arguments, without being obliged to employ calculations.
Every simple form being thus determined as member of a series, and furnished with its crystallographic sign; the combination containing those simple forms will be designated by writing the signs for the simple forms one after the other, as some instances in the preceding § 60. have already shown. As to the order in which the signs succeed each other in designating a combination, there are two distinct methods, each of which may be applied. Either those forms, whose planes are perpendicular to the axis, are set down first, those whose planes are parallel to it, last; the rest following each other according to the greater or less inclination which their faces have toward the axis, as decreasing from to ; or the forms, according to their kind, are collected into series between their limits, and then set down one after the other. The designation
represents fig. 26, according to the first method,
the same, after the second method.
70. Calculation of the Angles at the Edges of Combination.
After having developed the combination, the last office of crystallography is to calculate the angles of combination, or the incidences of the faces of different forms. In many instances this angle follows at once from those of the simple forms. If this will not do, crystallography employs general formulæ for the trigonometrical functions of the edge of combination, similar to those for the line of combination, containing equally the variable quantities and . The development of the combinations determines these quantities, and if substituted in the said formulæ, they give the value of a trigonometrical function, commonly of the co-sine of the angle, produced by two faces of different forms, meeting in the edge of combination.*
* For the preceding view of the New Crystallography we are indebted to Professor Mohs, who wrote it expressly for the present article.
Cleavage is the property which minerals possess of splitting in certain determinate directions. The faces or planes thus obtained, which are termed the faces of the cleavage, are more or less smooth and shining. The forms contained under these faces are called forms of cleavage, or cleavage-forms.
The cleavage-forms represent members of the series of crystallization of those mineral species to which the mineral having the cleavage belongs. The same may be inferred of such individuals or species as possess more than one cleavage-form. Hence cleavage extends the application of crystallography in the mineral kingdom, because a mineral, although it be not crystallized, may be cleavable, and thus allow the series, at least the system of crystallization, to be made out by cleavage in most of the cases, where no regular crystallizations occur.
The cleavage-forms are designated like those of crystallization. Cleavage-forms, Mohs remarks, if among the number of those, which in the preceding pages served as a basis to the derivation, are by preference chosen for representing the fundamental form in the species to which they belong; as in rhomboidal calc-spar, the rhomboid of . This rule, however, suffers an exception in the case of a rhomboid or a pyramid, which occur as cleavage-forms, being too obtuse or too acute. For this reason, in pyramidal copper pyrites, the fundamental form is P, though the cleavage-form is . No cleavage-form, whose dimensions are infinite, can be employed as a fundamental form.
A few technical expressions are employed by Mohs in determining the cleavage, of which the following may be enumerated. Cleavage, in the three first systems of crystallization, which are those of variable dimensions, is said to be axotomous,* when it appears as a single plane or face perpendicular to the axis; it is said to be paratomous,† if it is parallel to the faces of a finite form; and peritomous,‡ if it takes place parallel to the axis, and equally distinct in more than one direction. In the prismatic system, the expression prismatoidal means a single cleavage-face parallel to the axis; and diprismatic denotes the cleavage to be parallel at the same time to the faces of a vertical, and to those of a horizontal obliquangular four-sided prism. The expression monotomous, referring to the three systems, is more general than any of the foregoing; it comprises the axotomous and the prismatoidal, and is applied where a single cleavage-face is met with, whose position in regard to the axes, that is to say, whether it is parallel or perpendicular to the axis, has not been determined. The perfection or distinctness of the cleavage, which is next to be considered, refers to the aspect of the faces of the cleavage, viz. whether these are more or less smooth or shining, whether they are streaked, &c. The most important object to be remarked in this respect, is the sameness of quality existing in the faces belonging to one and the same, and the diver-
sity of faces belonging to different cleavage-forms; Mineralogy, the latter is a particular illustrated and confirmed by the derivations of the prismatic system. The nature of the faces of the cleavage is one of the means to remove the uncertainty mentioned in § 60, on account of the right rectangular prism. Lastly, it may be remarked, that we must be careful not to confound certain faces of composition (§ 86.), which sometimes likewise keep constant directions with the cleavage-forms.
The degrees of hardness or their limits are by Kirwan, Mohs, and others, expressed by numbers. The most precise scale of hardness is that of Mohs, in which the degrees are determined according to the following scale:
No. 1. denotes the degree of hardness of common talc and Venetian talc.
No. 2. is the hardness of a variety of prismatoidal gypsum, with an imperfect cleavage and imperfect transparency. Varieties perfectly transparent and crystallized are commonly too soft.
No. 3. Hardness of a cleavable variety of calcareous spar.
No. 4. Hardness of fluor spar.
No. 5. Hardness of apatite.
No. 6. Hardness of prismatic felspar.
No. 7. Hardness of rhomboidal quartz.
No. 8. Hardness of prismatic topaz.
No. 9. Hardness of rhomboidal corundum.
No. 10. Hardness of octahedral diamond.
We must obtain such specimens of the minerals just enumerated as will answer for the required purpose. If we wish by means of them to ascertain the hardness of a given mineral, we first try which of the members of the scale can be scratched by one of the corners of the given mineral. We begin with the highest member of the scale, and proceed till we arrive at one which can be scratched. We now compare the hardness of the given mineral with that of the first member of the scale which can be scratched, and with that next to it which is not scratched, by passing corners of each of the same shape over the surface of a hard and fine file. The resistance which the minerals oppose to the file, and the noise produced by rubbing pieces of a nearly equal shape, allow the relation of the hardness in the given mineral to be estimated. The degree of hardness found in this way is expressed by the numbers in the scale, and if these are not sufficient, by decimals; the distance between two subsequent members being supposed to be divided into ten square parts, without, however, maintaining those distances in reality everywhere to be equal. Thus, if hardness is designated by H, that of prismatic gypsum, for example, which is 2, will be expressed ; tourmaline, which has a hardness intermediate between that of rhomboidal quartz and prismatic topaz, will be expressed by 7.5.
* From αξον, the axis, and τμω, I cut; cleavable in one direction.
† From παρὰ, beside, and τμω, I cut; with cleavage planes, which are parallel with the planes of the fundamental figure, or are inclined to the axis.
‡ From περί, round about, and τμω, I cut; with surrounding cleavage planes parallel to the axis.
The specific gravity of minerals is determined by means of the hydrostatic balance, the hydrometer, and Adie's new instrument. Of these instruments, and the modes of using them, accounts are given in the Encyclopædia Britannica and Edinburgh Philosophical Journal.
II. CHARACTERS EMPLOYED IN THE DESCRIPTION OF THE SPECIES, SUB-SPECIES, KINDS, AND VARIETIES OF MINERALS.
- 1. Colour.—2. Common and Particular External Forms.—3. Distinct Connections.—4. Surface.—5. Lustre.—6. Fracture.—7. Shape of Fragments.—8. Transparency.—9. Opalescence.—10. Streak.—11. Soiling.—12. Tenacity.—13. Frangibility.—14. Flexibility.—15. Adhesion to the Tongue.—16. Unctuousity.—17. Smell.—18. Taste.
I. COLOUR.
The colours in the mineral kingdom are not so numerous as is generally imagined; and even the varieties, although often extremely beautiful, and apparently infinite in number, bear but a small proportion to the vast series that characterize the various productions of the vegetable and animal kingdoms. Werner, who bestowed great attention on this interesting and beautiful character, enumerates eight principal colours, viz. white, grey, black, blue, green, yellow, red, and brown. Each of these principal colours exhibits a greater or less number of varieties, many of which have been accurately defined, and are contained in the following enumeration.
1. Definitions of the different Varieties of Colour.
1. WHITE.
1. Snow-white is the purest colour, and nearly agrees with that of new-fallen snow. Examples of this colour occur in Carrara marble and common quartz.
2. Reddish-white is snow-white with a slight intermixture of red. Example, red quartz.
3. Yellowish-white is snow-white with very little lemon-yellow and ash-grey. Example, chalk.
4. Silver-white is yellowish-white with metallic lustre. Example, arsenical pyrites.
5. Greyish-white is snow-white mixed with a little ash-grey. Example, quartz.
6. Greenish-white is snow-white mixed with a very little emerald-green and ash-grey. Example, amianthus.
7. Milk-white is snow-white mixed with a little Berlin-blue and ash-grey. The colour of skimmed milk. Example, calcedony.
8. Tin-white differs from the preceding colour, principally in containing a little more grey, and having the metallic lustre. Example, native antimony.
2. GREY.
1. Lead-grey is ash-grey with a small portion of blue, and possesses metallic lustre. Example, lead-glance.
2. Bluish-grey is ash-grey mixed with a little blue. Example, limestone.
3. Pearl-grey is pale bluish grey intermixed with a little red. Example, porcelain jasper. Mineralogy.
4. Smoke-grey, or brownish-grey, is dark bluish grey mixed with a little brown. Example, flint.
5. Greenish-grey is ash-grey mixed with a little emerald-green, and has sometimes a faint trace of yellow. Example, clay-slate.
6. Yellowish-grey is ash-grey mixed with lemon-yellow and a minute trace of brown. Example, calcedony.
7. Ash-grey is the characteristic colour. It is the colour of wood ashes. Example, quartz.
8. Steel-grey is dark ash-grey with metallic lustre. It is the colour of newly broken steel. Example, native platina.
3. BLACK.
1. Greyish-black is velvet-black mixed with ash-grey. Example, basalt.
2. Iron-black is principally distinguished from the preceding by its being rather darker, and possessing a metallic lustre. Example, magnetic iron-ore.
3. Velvet-black is the characteristic colour of this series. It is the colour of black velvet. Example, obsidian.
4. Pitch-black, or brownish-black, is velvet-black mixed with a little yellowish-brown. Example, cobalt ochre.
5. Greenish-black, or raven-black, is velvet-black mixed with a little greenish-grey. Example, hornblende.
6. Bluish-black is velvet-black mixed with a little blue. Example, black earthy cobalt ochre.
4. BLUE.
1. Blackish-blue is Berlin-blue mixed with much black, and a trace of red. Example, blue copper.
2. Azure-blue is Berlin-blue mixed with a little red. Example, blue copper.
3. Violet-blue is Berlin-blue mixed with much red and very little black. Example, amethyst.
4. Lavender-blue is violet-blue mixed with a small portion of grey. Examples, lithomarge and porcelain jasper.
5. Plum-blue is Berlin-blue, with more red than in violet-blue, and a small portion of brown and black. Example, spinel.
6. Berlin-blue is the purest or characteristic colour of the series. Examples, sapphire, rock-salt, kyanite.
7. Smalt-blue is Berlin-blue, with much white, and a trace of green. Examples, pale-coloured smalt, named eschel, earthy blue iron, earthy blue copper, and some varieties of gypsum.
8. Duck-blue is a dark blue colour, composed of blue, much green, and a little black. Example, ceylanite.
9. Indigo-blue is a deep blue colour, composed of blue, with a considerable portion of black, and a little green. Example, earthy blue iron of Eckardsberg, in Thuringia.
10. Sky-blue is a pale blue colour, composed of blue, green, and a little white. It is the colour of a clear sky, hence its name. Example, lenticular copper.
1. Verdigris-green is emerald-green mixed with much Berlin-blue and a little white. Example, copper-green and green Siberian felspar.
2. Celandine-green is verdigris-green mixed with ash-grey. Examples, green earth, Siberian and Brazilian beryl.
3. Mountain-green is emerald-green mixed with much blue, and a little yellowish-grey; or verdigris-green with yellowish-grey. Examples, beryl and glassy actinolite.
4. Leek-green is emerald-green, with bluish-grey and a little brown. Examples, nephrite and common actinolite.
5. Emerald-green is the characteristic or pure unmixed green. Example, emerald.
6. Apple-green is emerald-green mixed with a little greyish-white. Example, chrysoptile.
7. Grass-green is emerald-green mixed with a little lemon yellow. Example, uranite.
8. Blackish-green is pistachio-green mixed with a considerable portion of black. Example, augite.
9. Pistachio-green is emerald-green mixed with more yellow than in grass-green, and a small portion of brown. Examples, chrysolite and epidote.
10. Asparagus-green is pistachio-green mixed with a little greyish white; or emerald-green mixed with yellow and a little brown. Examples, garnet, olivenite, and beryl.
11. Olive-green is grass-green mixed with much brown, and a little grey. Examples, common garnet, olivenite, and pitch-stone.
12. Oil-green is emerald-green mixed with yellow, brown, and grey; or pistachio-green, with much yellow and light ash-grey. Examples, fuller's-earth and beryl.
13. Siskin-green is emerald-green mixed with much lemon-yellow and a little white. Example, uran mica.
1. Sulphur-yellow is lemon-yellow mixed with much emerald-green and white. Example, native sulphur.
2. Brass-yellow differs from the preceding yellow principally in having metallic lustre; it contains a small portion of grey. Example, copper pyrites.
3. Straw-yellow is sulphur-yellow mixed with much greyish-white. Example, yellow cobalt ochre.
4. Bronze-yellow is brass-yellow mixed with a little steel-grey and a minute portion of reddish-brown. Example, iron pyrites.
5. Wax-yellow is lemon-yellow mixed with reddish-brown and a little ash-grey; or it may be considered as honey-yellow with greyish-white. Examples, opal and yellow lead-spar.
6. Honey-yellow is sulphur-yellow mixed with chesnut-brown. Examples, fluor-spar and beryl.
7. Lemon-yellow is the pure unmixed colour. It is the colour of the rind of ripe lemons. Example, yellow orpiment.
8. Gold-yellow is the preceding colour with metallic lustre. Example, native gold.
9. Ochre-yellow is lemon-yellow mixed with a considerable quantity of light chesnut-brown. Examples, yellow earth and jasper.
10. Wine-yellow is lemon-yellow mixed with a
small portion of red and greyish-white. Examples, Saxon and Brazilian topaz. Mineralogy.
11. Cream-yellow, or Isabella-yellow, contains more red and grey than the wine-yellow, and also a little brown. Examples, bole from Strigau and compact limestone.
12. Orange-yellow is lemon-yellow with carmine-red. It is the colour of the rind of the ripe orange. Example, uran-ochre.
1. Aurora, or morning-red, is carmine-red mixed with much lemon-yellow. Example, red orpiment.
2. Hyacinth-red is carmine-red mixed with lemon-yellow, and a minute portion of brown; or aurora-red mixed with a minute portion of brown. Examples, hyacinth and tile-ore.
3. Tile-red is hyacinth-red mixed with greyish-white. The colour of tiles or bricks. Example, porcelain jasper.
4. Scarlet-red is carmine-red mixed with a very little lemon-yellow. Example, light-red cinnabar from Wolfstein.
5. Blood-red is scarlet-red mixed with a small portion of black. Examples, pyrope and jasper.
6. Flesh-red is blood-red mixed with greyish-white. Examples, felspar and calc-spar.
7. Copper-red scarcely differs from the preceding variety, but in possessing metallic lustre. Example, native copper.
8. Carmine-red is the characteristic colour. Example, spinel, particularly in thin splinters.
9. Cochineal-red is carmine-red mixed with bluish-grey. Example, dark-red cinnabar.
10. Crimson-red is carmine-red mixed with a considerable portion of blue. Example, oriental ruby.
11. Columbine-red is carmine-red with more blue than the preceding variety, and, what is characteristic for this colour, a little black. Example, precious garnet.
12. Rose-red is cochineal-red mixed with white. Examples, red manganese and quartz.
13. Peach-blossom-red is crimson-red mixed with white. Example, red cobalt-ochre.
14. Cherry-red is crimson-red mixed with a considerable portion of brownish-black. Examples, spinel, red antimony, and precious garnet.
15. Brownish-red is blood-red mixed with brown. Example, clay iron-stone.
1. Reddish-brown is chesnut-brown mixed with a little red and yellow; or chesnut brown with a small portion of aurora-red. Example, brown-blende from the Hartz.
2. Clove-brown is chesnut-brown mixed with cochineal-red and a little black. It is the colour of the clove. Examples, rock-crystal and brown hematite.
3. Hair-brown is clove-brown mixed with ash-grey. Example, wood-opal.
4. Broccoli-brown is chesnut-brown mixed with much blue, and a small portion of green and red. Example, zircon.
Mineralogy. 5. Chesnut-brown is the characteristic or pure brown colour. Example, Egyptian jasper.
6. Yellowish-brown is chesnut-brown mixed with a considerable portion of lemon-yellow. Examples, iron-flint and jasper.
7. Pinchbeck-brown is yellowish-brown with metallic lustre. Rather the colour of tarnished pinchbeck. Example, mica.
8. Wood-brown is yellowish-brown mixed with much pale ash-grey. Examples, mountain wood and bituminous wood.
9. Liver-brown is chesnut-brown mixed with olive-green and ash-grey. The colour of boiled liver. Example, common jasper.
10. Blackish-brown is chesnut-brown mixed with black. Examples, mineral pitch from Neufchatel and moor coal.
II. The Play of the Colours.
If we look on a mineral which possesses this property, we observe, on turning it slowly, besides its common colours, many others, which are bright, change very rapidly, and are distributed in small spots. We observe it in the diamond when cut, and in precious opal.
III. The Changeability of the Colours.
When the surface of a mineral, which we turn in different directions, exhibits, besides its common colours, different bright colours, that do not change so rapidly, are fewer in number, and occur in larger patches than in the play of the colour, it is said to exhibit what is called the changeability of the colours. The changeability of colour is seen only in particular directions, the play of colour in all directions.
We distinguish two kinds of this phenomenon.
1st, That which is observed by looking in different positions on the mineral, as in Labrador felspar.
2d, That observed by looking through it, as in the common opal, which shows a milk-white colour when we look on its surface, but when held between the eye and the light is wine-yellow.
IV. The Iridescence.
When a mineral exhibits the colours of the prism or the rainbow, arranged in parallel, and sometimes variously curved layers, it is said to be iridescent. It is to be observed by,
1st, Looking on the mineral only, as in precious opal, adularia, &c.
2d, Both by looking on the mineral and through it, as in calcareous spar crossed by thin veins, some aragonites, rainbow calcedony, and some amethysts.
V. Tarnished Colours.
A mineral is said to be tarnished when it shows on its external surface, or on that of the distinct concretions; fixed colours different from those on its interior or fresh fracture.
Tarnished colours are simple or variegated.
I. Simple.
a. Grey,—white cobalt.
b. Black,—native arsenic.
c. Brown,—magnetic pyrites.
d. Reddish,—native bismuth.
II. Variegated.
The variegated, or party-coloured, are distinguished according to the colour of their basis. Of these the following are enumerated in the tabular view.
a. Pavonine, or peacock-tail tarnish. This is an assemblage of yellow, green, blue, red, and brown colours, on a yellow ground. The colours are nearly equal in proportion, and are never precisely distinct, but always pass more or less into one another. Example, copper pyrites.
b. Iridescent, or rainbow tarnish. In this variety the colours are red, blue, green, and yellow, on a grey ground. It is more beautiful and brighter than the preceding. Example, specular iron-ore or iron-glance of Elba.
c. Columbine, or pigeon-neck tarnish. The colours are the same as in the preceding, with this difference, that the tints of colour are paler, and the red predominates. Example, native bismuth of Schneeberg.
d. Tempered-steel tarnish. It consists of very pale blue, red, green, and very little yellow, on a grey ground. Example, grey cobalt.
II. COMMON AND PARTICULAR EXTERNAL FORMS
1. Common External Shape.
Common external shapes are those in which there are neither a determinate number of planes meeting under determinate angles, nor any resemblance to known natural or artificial bodies. As they occur more frequently than the other shapes, they are named Common external shapes.
Six different kinds are enumerated by Werner, which are distinguished according to their relative length, breadth, and thickness, their relative magnitude, and their connections with other minerals. The kinds are massive, disseminated, in angular pieces, in grains, in plates, and in membranes.
1. Massive is that common external shape which is from the size of a hazel-nut to the greatest magnitude, and whose dimensions, in length, breadth, and thickness, are nearly alike. It occurs imbedded in other minerals, and it is intermixed with them at their line of junction. Example, Galena or lead-glance.
2. Disseminated is from the size of a hazel-nut until it is scarcely visible, and its dimensions, in length, breadth, and thickness, are nearly alike. It is imbedded, and is intermixed with the inclosing mineral at the line of junction.
3. In angular pieces. Minerals having an angular shape, in which the length, breadth, and thickness are nearly alike, which are found loose, or slightly imbedded, and without any intermixture with the inclosing mineral at the line of junction, and from the size of a hazel-nut and upwards, are said to occur in angular pieces. It is distinguished from the massive by its occurring either loose, or not intermixed with the basis at the line of junction. Of this external shape there are two kinds:
a. Sharp-cornered, as in quartz.
b. Blunt-cornered, as in common opal.
Mineralogy. 4. In grains. Minerals having a roundish form, and imbedded or loose, and not much larger than a hazel-nut, are said to occur in grains.
5. In plates. Minerals which occur in external shapes, whose length and breadth are great in comparison of their thickness, in which the thickness is not equal throughout, and is so considerable as to allow the fracture to be distinguished, are said to occur in plates. The maximum thickness of plates is half an inch. Example, red silver.
6. In membranes or flakes. This shape is distinguished from the former by its thinness, as it never greatly exceeds the thickness of common paper, and the fracture cannot be seen. Example, iron pyrites.
II. PARTICULAR EXTERNAL SHAPE.
Particular external shapes differ from the common external shapes, in bearing a resemblance to natural or artificial bodies, and in being far more characteristic and varied in their aspect. There are four different sets, entitled, longish, roundish, flat, and cavernous.
1. Longish particular external shapes.
a. Dentiform. Adheres by its thick extremity, and becomes gradually thinner, incurvated, and at length terminates in a free point, so that it resembles a canine tooth, whence its name. Example, native silver.
b. Filiform. Adheres by its thicker extremity, and terminates by an almost imperceptible diminution of thickness, and is usually curved in different directions. It is thinner and longer than the dentiform. Example, native silver.
c. Capillary. When the filiform becomes longer and thinner, it forms the capillary. It is generally much entangled, and sometimes the threads are so near each other that it passes into the compact. Example, native silver.
d. Reticulated is composed of many straight threads, which are sometimes parallel and sometimes meet each other at right angles, and form a net-like shape. Example, native silver.
e. Dendritic. In this external shape we can observe a trunk, branches, and twigs, which are distinguished from each other by their thickness, the trunk being the thickest. Example, native copper.
f. Coralloidal. When two or three branches, having rounded or pointed extremities, proceed from one stem, the coralloidal external shape is formed. There are usually many stems together. Example, calc-sinter.
g. Stalactitic. A mineral is said to possess a stalactitic external shape, when it consists of different straight, more or less lengthened rods, which are thickest at their attachment, and become narrower at their free extremity, which is rounded or pointed. Example, calc-sinter.
h. Cylindrical consists of long, rounded, straight, imperforated, usually parallel rods, which are attached at both extremities, and are generally thicker at the extremities than the middle. The interstices are either empty or filled up with another mineral. Example, galena or lead-glance.
i. Tubiform consists of long, usually single,
perforated tubes, which are somewhat longitudinally knotty. Example, calc-sinter.
k. Claviform is the reverse of stalactitic; it is composed of club-shaped parallel rods, which adhere by their thin extremities. Example, compact black hematite.
l. Fruticose. This external shape has the appearance of cauliflower. Example, calc-sinter.
2. Roundish Particular External Shapes.
a. Globular. Under this are comprehended:
a. Perfect globular or spherical, as in alum-slate.
β. Imperfect globular, as in calcedony.
γ. Ovoidal or elliptical. Examples, rounded masses of quartz in puddingstone.
δ. Spheroidal. When the spherical is compressed the spheroidal is formed. Example, Egyptian jasper.
ε. Amygdaloidal. When the ovoidal is compressed in the direction of its length, the amygdaloidal is formed. Example, zeolite.
b. Botryoidal consists of large segments of small balls, which are irregularly heaped together, and have many interstices. It resembles grapes, whence its name. Example, hematite.
c. Reniform consists of small segments of large balls, which are so closely set together, that no interstices are formed. Example, calcedony.
d. Tuberculate. This shape consists of irregular roundish or longish elevations and depressions. Example, flint.
e. Fused-like or liquiform. This consists of numerous very flat rounded elevations, which are generally depressed in the middle. Example, lead-glance.
3. Flat Particular External Shapes.
a. Specular has on one side, seldom on two opposite sides, a straight smooth shining surface. It occurs in veins. Example, galena or lead-glance.
b. In leaves. In this external shape there are thin leaves, which are either irregularly curved, or are straight, and have throughout the same thickness. It occurs frequently in native gold.
4. Cavernous Particular External Shapes.
a. Cellular. A mineral is said to be cellular, when it is composed of straight or bent tables, which cross each other in such a manner as to form empty spaces or cells. Example, quartz.
b. Impressed. That is, when one mineral shows the impression of any particular or regular external shape of another mineral. It borders on the cellular shape, and is formed when a newer mineral is deposited over an older, the form of which it assumes, and retains even after the impressing mineral has been destroyed or removed.
c. Perforated consist of long vermicular cavities, which occupy but an inconsiderable portion of the mass, and terminate on the surface in small holes. When the holes become very numerous, it passes into spongy form. Example, bog iron-ore.
d. Corroded. A mineral is said to be corroded when
Mineralogy. it is traversed with numerous hardly perceptible roundish holes. Example, quartz.
c. Amorphous is composed of numerous roundish and angular parts that form inequalities, between which there are equally irregular hollows. Example, silver-glance or sulphuretted silver.
f. Vesicular. When a mineral has distributed through its interior many single, usually round, elliptical, and spheroidal, also amygdaloidal, or irregularly-shaped cavities, it is said to be vesicular. Example, wacke and lava.
III. DISTINCT CONCRETIONS.
Distinct concretions are those parts into which minerals are naturally divided, and which can be separated from one another, without breaking through the solid or fresh part of the mineral. In describing them, we have to attend to the following appearances. 1. Their shape; 2. Their surface; and, 3. Their lustre.
1. Shape of the Distinct Concretions.
They are granular, lamellar, prismatic, radiated, and fibrous.
1. Granular distinct concretions are those in which the length, breadth, and thickness, are nearly alike. Primitive limestone or marble is composed of granular distinct concretions.
2. Lamellar distinct concretions are those in which the length and breadth are nearly equal, and much more considerable than the thickness. Lamellar heavy-spar affords a good example of this kind of concretion.
3. Prismatic distinct concretions are those in which the length is very considerable, in comparison of the thickness, or in the form of irregular prisms. Examples, amethyst and prismatic heavy spar.
4. Radiated distinct concretions are those in which the form is then prismatic, differing from the preceding in being narrower, and in having the form of rays. The radiated fracture of Werner belongs to this division. Example, radiated iron pyrites.
5. Fibrous distinct concretions are those in form of fibres. The fibrous fracture of Werner is included under this head. Example, actinolite.
2. Surface of the Distinct Concretions.
The surface varies considerably; in some it is smooth, as in hematite; in others it is streaked, as in schorl, or it is uneven, as in hornblende.
3. Lustre of the Distinct Concretions.
Here the varieties of lustre are the same as already enumerated, and therefore require no particular illustration.
IV. SURFACE.
The following are the varieties of this character:
1. Uneven. This, of all the kinds of external surface, presents the greatest and most irregular elevations and depressions, yet they are not so considerable as to alter the external shape. Example, surface of balls of calcedony.
2. Granulated. When the surface appears like shagreen, it is said to be granulated. Mineralogy.
3. Rough. This kind of surface is marked with small scarcely visible elevations, which we can hardly discover but by the feel. It has little or no lustre. Example, rolled pieces of common quartz.
4. Smooth. Here there is no perceptible inequality, and the surface reflects more light than the preceding kinds of external surface. Example, fluor-spar.
5. Streaked. This kind of surface is marked with line-like elevations. It is either simply streaked or doubly streaked.
a. Simply streaked, when the line-like elevations run but in one direction.
a. Longitudinally streaked. When the streaks are parallel with the length of the lateral planes. Example, topaz.
β. Transversely streaked. When the streaks are parallel with the breadth of the lateral planes. Example, rock-crystal.
γ. Diagonally streaked. When the streaks are parallel with the diagonal of the planes. Example, garnet.
δ. Alternately streaked. When transverse and longitudinal streaks occur on alternate planes. Example, cubic iron-pyrites.
b. Doubly streaked, when the streaks run in different directions. This is of two kinds.
a. Plumiformly. When the streaks run obliquely towards a principal streak, like the disposition of the parts of a feather. Example, plumose native bismuth.
β. Reticularly. When the streaks either cross each other in a promiscuous manner, or under right angles, forming a kind of flat net-work. Example, silver-white cobalt.
c. Drusy. When a crystal is coated with a number of minute crystals of the same kind as the mineral itself, so that the new surface acquires a scaly aspect, it is denominated drusy. Example, common iron-pyrites.
V. LUSTRE.
Here we have to consider the intensity and the sort of lustre.
1. The Intensity of the Lustre. Of this there are five different degrees.
1. Splendent. A fossil is said to be splendid, when in full day-light (not in the sun-shine) it is visible at a great distance. Example, galena or lead-glance.
2. Shining. When a mineral at a distance reflects but a weak light, it is said to be shining. Example, heavy-spar.
3. Glistening. This degree of lustre is only observable when the mineral is near us, and at no greater distance than arms-length. Example, porcelain-jasper.
4. Glimmering. If the surface of a mineral, when held near to the eye in full and clear day-light, presents a very great number of small faintly shining points, it is said to be glimmering. Example, red hematite.
Mineralogy. 5. Dull. When a mineral does not reflect any light, or is entirely destitute of lustre, it is said to be dull. Example, chalk.
2. The Sort of Lustre.
The following are the different kinds of lustre:
1. Metallic lustre, which is always combined with opacity. It is divided into perfect and imperfect. The perfect occurs in native metals, the imperfect in tantalum ore.
2. Adamantine. Of this lustre there are two varieties, viz. metallic adamantine, and common adamantine. White lead spar is an example of the first, and diamond of the second.
3. Pearly is divided into common and metallic-like. Mica is an example of the first, and schiller-spar of the second.
4. Resinous or waxy. Example, pitch-stone.
5. Vitreous or glassy. Example, rock-crystal.
VI. THE FRACTURE.
Fracture surfaces, or planes, are those produced on breaking a mineral. The following are the principal kinds:
1. Splintery. When, on a nearly even fracture surface, small wedge-shaped or scaly parts are to be observed, which adhere by their thicker ends, and allow light to pass through, we say that the fracture is splintery. It sometimes passes into even. Example, quartz.
2. Even is that kind of fracture in which the surface is nearly even, or without inequalities. Example, Lydian-stone.
3. Conchoidal is composed of concave and convex roundish depressions and elevations, which are more or less regular. When regular, they are accompanied with concentric ridges, as in many shells, and hence present a conchoidal appearance. Example, obsidian.
4. Uneven. In this kind of fracture the surface is marked with numerous angular elevations. These inequalities are termed the grain, so that we have coarse and fine-grained uneven fractures. Example, copper-pyrites.
5. Earthy. When the fracture-surface shows a great number of very small elevations and depressions, which make it appear rough, it is called earthy. Example, chalk.
6. Hackly. When the fracture-surface consists of numerous small slightly-bent sharp inequalities, it is said to be hackly. Example, native copper.
7. Slaty. In this kind of fracture the mineral splits into tables or slates which are more or less perfect. Example, common roof-slate.
VII. THE SHAPE OF THE FRAGMENTS.
Frragments are those shapes which are formed when a mineral is so forcibly struck, that masses, having surrounding fracture-surfaces, are separated from it.
The fragments are either regular or irregular.
1. Regular fragments are inclosed in a certain number of regular planes, that meet under determinate angles. The following are the varieties of regular fragments:
1. Cubic, which occur in minerals possessing a rectangular three-fold cleavage, as galena, or lead-glass, and rock-salt.
2. Rhombohedral, or oblique-angular, which occur in minerals having a three-fold cleavage, as calcareous-spar.
3. Tetrahedral, or three-sided pyramidal and octahedral, occur in minerals having a four-fold cleavage, in which the folia meet under equal angles, as in fluor-spar.
4. Dodecahedral. Fragments of this form occur in minerals having a six-fold cleavage. Example, rock-crystal.
II. Irregular fragments are such as have no regular form. The following are the different varieties:
1. Cuneiform, in which the breadth and thickness are much less than the length, and gradually and regularly diminish in magnitude from one end to the other. Example, radiated zeolite.
2. Splintery, in which the breadth and thickness are less considerable than the length, but without diminution of magnitude from one extremity to the other. Example, asbestos.
3. Tabular, in which the breadth and length are more considerable than the thickness. Example, clay-slate.
4. Indeterminate angular, in which the length, breadth, and thickness, are in general nearly alike, but the edges differ much in regard to sharpness, which gives rise to the following distinctions:
- Very sharp-edged, as in obsidian.
- Sharp-edged, as in common quartz.
- Rather sharp-edged, as in basalt.
- Rather blunt-edged, as in pumice.
- Blunt-edged, as in gypsum.
- Very blunt-edged, as in loam.
VIII. THE TRANSPARENCY.
This character presents the five following degrees:
1. When a mineral, either in thick or thin pieces, allows the rays of light to pass through it so completely, that we can clearly distinguish objects placed behind it, it is said to be transparent. It is either simply transparent, that is, when the body seen through it appears single, as in mica and selenite; or duplicating, when the body seen through it appears double, as in calcareous-spar.
2. Semi-transparent. When objects can be discerned only through a thin piece, and then always appear as if seen through a cloud. Example, calcedony.
3. Translucent. When the rays of light penetrate into the mineral and illuminate it, but objects cannot be observed either through thick or thin pieces, it is said to be translucent. Example, pitch-stone.
4. Translucent on the edges. When light shines through the thinnest edges and corners, or when the edges are illuminated in the same degree as the whole mineral in the immediately preceding variety of transparency, it is said to be translucent on the edges. Example, hornstone.
5. Opaque. When, even on the thinnest edges of a mineral, no light shines through, it is said to be opaque, as in chalk.
Some minerals, when held in particular directions, reflect from single spots in their interior, a coloured shining lustre, and this is what is understood by opalescence.
By the streak we understand the appearance which minerals exhibit when scratched or rubbed with a hard body, as a knife or steel. In some instances, the colour of the mineral is changed; in others, the lustre, and frequently neither colour nor lustre are altered.
When a mineral, taken between the fingers, or drawn across another body, leaves some particles, or a trace, it is said to soil or colour.
By tenacity is understood the relative mobility, or the different degrees of cohesion of the particles of minerals. The degrees of tenacity are the following:
1. Brittle. A mineral is said to be brittle, when, on cutting it with a knife, it emits a grating noise, and the particles fly away in the form of dust, and leave a rough surface, which has in general less lustre than the fracture. Example, quartz.
2. Sectile or Mild. On cutting minerals possessing this degree of tenacity, the particles lose their connection in a considerable degree, but this takes place without noise, and they do not fly off, but remain on the knife. Example, galena or lead-glance.
3. Ductile. Minerals possessing this degree of tenacity can be cut into slices with a knife, and extended under the hammer. Example, native gold.
By frangibility is understood the resistance which minerals oppose, when we attempt to break them into pieces or fragments. It must not be confounded with hardness. Quartz is hard, and hornblende comparatively soft; yet the latter is much more difficultly frangible than the former.
This term expresses the property possessed by some minerals, of bending without breaking. Flexible minerals are either elastical flexible, that is, if when bent they spring back again into their former direction, as mica; or common flexible, when they can be bent in different directions without breaking, and remain in the direction in which they have been bent, as molybdena, gypsum, talc, asbestos, and all malleable minerals.
This character occurs only in such minerals as possess the property of absorbing moisture, which causes them to adhere to the tongue. Example, meerschaum.
Some minerals feel greasy, others meagre; and in
order to distinguish the different degrees of greasiness, the following distinctions are employed:
- 1. Very greasy, as talc and graphite.
- 2. Greasy, as steatite and fuller's earth.
- 3. Rather greasy, as asbestos and polished serpentine.
- 4. Meagre, as cobalt.
Of this we can give no definition, and shall therefore illustrate it by the minerals in which it occurs. It is observed under the three following circumstances:
- 1. Spontaneously emitted; in which case it is.
- a. Bituminous, as mineral oil and mineral pitch.
- b. Faintly sulphureous, as natural sulphur.
- c. Faintly bitter, as radiated grey antimony.
- 2. After breathing on it, in which a clayey-like smell is produced, as in hornblende and chlorite.
- 3. Excited by friction.
- a. Urinous, in stink-stone.
- b. Sulphureous, in iron-pyrites.
- c. Garlick-like, or arsenical, in native arsenic and arsenic-pyrites.
- d. Empyreumatic, in quartz and rock-crystal.
This character occurs principally in the saline class, for which it is highly characteristic.
The varieties of it are,
- 1. Sweetish taste, common salt.
- 2. Sweetish astringent, natural alum and rock butter.
- 3. Styptic, blue and green vitriol.
- 4. Salty bitter, natural Epsom salt.
- 5. Salty cooling, nitre.
- 6. Alkaline, natural soda.
- 7. Urinous, natural sal-ammoniac.
- 1. Pure Hydrogen Gas.
- 2. Carburetted Hydrogen Gas.
- 3. Sulphuretted Hydrogen Gas.
- 4. Phosphuretted Hydrogen Gas.
- 1. Pure Atmospheric Air.
- 1. Pure Atmospheric Water.
- 1. Common Sea Water.
- 1. Aeriform Carbonic Acid.
- 1. Aeriform Muriatic Acid.
- 1. Aeriform Sulphuric Acid.
2. Liquid Sulphuric Acid.
Genus IV. BORACIC ACID.
- 1. Prismatic Boracic Acid.
Genus V. ARSENIC ACID.
- 1. Octahedral Arsenic Acid.
Order IV.—SALT.
Genus I. NATRON.
- 1. Prismatic Natron.
Genus II. GLAUBER SALT.
- 1. Prismatic Glauber Salt.
Genus III. NITRE.
- 1. Prismatic Nitre.
Genus IV. ROCK SALT.
- 1. Hexahedral Rock Salt.
Genus V. SAL-AMMONIAC.
- 1. Octahedral Sal Ammoniac.
Genus VI. VITRIOL.
- 1. Hemiprismatic Vitriol, or Green Vitriol.
- 2. Prismatic Vitriol, or Blue Vitriol.
- 3. Pyramidal Vitriol, or White Vitriol.
Genus VII. EPSOM SALT.
- 1. Prismatic Epsom Salt.
Genus VIII. ALUM.
- 1. Octahedral Alum.
Genus IX. BORAX.
- 1. Prismatic Borax.
Genus X. GLAUBERITE.
- 1. Prismatic Glauberite.
Genus I. GYPSUM.
- 1. Prismatic Gypsum, or Common Gypsum.
- 2. Prismatic Gypsum, or Anhydrite.
Genus II. CRYOLITE.
- 1. Prismatic Cryolite.
Genus III. ALUM STONE.
- 1. Rhomboidal Alum Stone.
Genus IV. FLUOR.
- 1. Octahedral Fluor.
Genus V. APATITE.
- 1. Rhomboidal Apatite.
Genus VI. LIMESTONE.
- 1. Prismatic Limestone, or Arragonite.
- 2. Rhomboidal Limestone.
- 3. Macrotypous Limestone.
- 4. Brachytypous Limestone, or Rhomb-Spar.
Genus I. SPARRY IRON.
- 1. Rhomboidal Sparry Iron.
- * Spherosiderite.
Genus II. RED MANGANESE.
- 1. Rhomboidal Red Manganese.
- * Manganese Spar.
Genus III. CALAMINE.
- 1. Prismatic, or Electric Calamine.
- 2. Rhomboidal Calamine.
Genus IV. TUNGSTEN, or SCHEELIUM.
- 1. Pyramidal Tungsten.
- 1. Pyramido-prismatic Baryte, or Strontianite.
- 2. Di-Prismatic Baryte, or Witherite.
- 3. Prismatic Baryte, or Heavy-Spar.
- 4. Prismatic Baryte, or Celestine.
- 1. Di-Prismatic Lead-Spar, or White and Black Lead-Spar.
- 2. Rhomboidal Lead-Spar, or Green and Brown Lead-Spar.
- 3. Hemiprismatic Lead-Spar, or Red Lead-Spar.
- 4. Pyramidal Lead-Spar, or Yellow Lead-Spar.
- 5. Prismatic Lead-Spar, or Sulphate of Lead.
- * 1. Corneous Lead-Spar.—2. Arseniate of Lead.—3. Plomb Gomme.
Genus I. CORNEOUS SILVER.
- 1. Hexahedral Corneous Silver.
Genus II. CORNEOUS MERCURY.
- 1. Pyramidal Corneous Mercury.
Genus I. COPPER GREEN.
- 1. Uncleavable Copper Green.
Genus II. LIRICONITE.
- 1. Prismatic Liriconite, or Lenticular Arseniate of Copper.
- 2. Hexahedral Liriconite, or Cubical Arseniate of Iron.
Genus III. OLIVENITE.
- 1. Prismatic Olivenite, or Prismatic Arseniate of Copper.
- 2. Di-Prismatic Olivenite.
Genus IV. BLUE MALACHITE, or BLUE COPPER.
- 1. Prismatic Blue Malachite.
- * Velvet Blue Copper.
Genus V. EMERALD MALACHITE.
- 1. Rhomboidal Emerald Malachite.
Genus VI. GREEN MALACHITE.
- 1. Prismatic Green Malachite, or Phosphate of Copper.
- 2. Di-Prismatic Green Malachite, or Common Malachite.
* ATACAMITE.
- 1. Prismatic Atacamite, or Muriate of Copper.
Genus I. COPPER-MICA.
- 1. Rhomboidal Copper-Mica, or Micaeous Arseniate of Copper.
- 2. Prismatic Copper-Mica.
Genus II. URAN-MICA, or URANITE.
- 1. Pyramidal Uran-Mica.
- * Uran-Ochre.
Genus III. COBALT-MICA, or RED COBALT.
- 1. Prismatic Red Cobalt.
* COBALT-OCHRE.
- 1. Black Cobalt-Ochre.
Mineralogy. Genus III. RED COPPER-ORE.
1. Octahedral Red Copper-Ore.
Genus IV. TIN-ORE.
1. Pyramidal Tin-Ore.
Genus V. WOLFRAM-ORE.
1. Prismatic Wolfram.
Genus VI. TANTALUM-ORE.
1. Prismatic Tantalum-Ore.
* Tantalite.
Genus VII. URANIUM-ORE.
1. Uncleavable Uranium-Ore.
Genus VIII. CERIUM-ORE.
1. Uncleavable Cerium-Ore.
* Allanite, or Prismatic Cerium-Ore.
** Cerin.
Genus IX. CHROME-ORE.
1. Prismatic Chrome-Ore, or Chromat of Iron.
Genus X. IRON-ORE.
1. Octahedral Iron-Ore, or Magnetic Iron-Ore.
* Titanitic Iron-Ore. ** Iserrine.
*** Menachanite.
2. Rhomboidal Iron-Ore, or Red Iron-Ore.
3. Prismatic Iron-Ore, or Brown Iron-Ore.
* Bog Iron-Ore. ** Lievrte.
Genus XI. MANGANESE ORE.
1. Prismatic Manganese-Ore, or Black Manganese.
* Scaly Brown Manganese-Ore.
2. Prismatoidal Manganese-Ore, or Grey Manganese.
* 1. Earthy Grey and Brown Manganese-Ore, or Wad.—2. Phosphat of Manganese.
Order IX.—NATIVE METALS.
Genus I. ARSENIC.
1. Native Arsenic.
Genus II. TELLURIUM.
1. Native Tellurium.
Genus III. ANTIMONY.
1. Dodecahedral Antimony.
2. Prismatic Antimony, or Antimonial Silver.
Genus IV. BISMUTH.
1. Octahedral Bismuth.
Genus V. MERCURY.
1. Liquid Native Mercury.
2. Dodecahedral Mercury, or Native Amalgam.
Genus VI. SILVER.
1. Hexahedral Silver.
Genus VII. GOLD.
1. Hexahedral Gold.
Genus VIII. PLATINA.
1. Native Platina.
Genus IX. IRON.
1. Octahedral Iron.
1. Subsp. Terrestrial Native Iron.
2. — Meteoric Native Iron.
Genus X. COPPER.
1. Octahedral Copper.
* 1. Osmium.—2. Palladium.—3. Mineralogy. Nickel.
Genus I. NICKEL PYRITES, or COPPER-NICKEL.
1. Prismatic Nickel Pyrites.
* Nickel Ochre.
** Black Nickel.
Genus II. ARSENIC PYRITES.
1. Axotomous Arsenic Pyrites.
2. Prismatic Arsenic Pyrites.
Genus III. COBALT PYRITES.
1. Hexahedral Cobalt-Pyrites, or Silver-White Cobalt.
2. Octahedral Cobalt-Pyrites, or Tin-White Cobalt.
* Grey Cobalt Pyrites.
** Cobalt-Kies.
*** Radiated Tin-White Cobalt Pyrites.
Genus IV. IRON PYRITES.
1. Hexahedral Iron-Pyrites.
2. Prismatic Iron-Pyrites.
3. Rhomboidal Iron-Pyrites, or Magnetic Pyrites.
Genus V. COPPER-PYRITES.
1. Pyramidal Copper-Pyrites, or Yellow Copper-Pyrites.
Undetermined Pyrites.
* 1. Nickeliferous Grey Antimony.—2. Common Tin Pyrites.
Genus I. COPPER-GLANCE.
1. Tetrahedral Copper-Glance, or Grey and Black Copper.
2. Prismatoidal Copper-Glance.
3. Prismatic Copper-Glance, or Vitreous Copper.
* 1. Variegated Copper.—2. Argentiferous Copper-Glance.—3. Plumbiferous Copper-Glance.—4. Tennantite.—5. Eukairite.
Genus II. SILVER-GLANCE, or VITREOUS SILVER.
1. Hexahedral Silver-Glance.
Genus III. GALENA, or LEAD-GLANCE.
1. Hexahedral Galena, or Lead-Glance.
* Blue Lead.
Genus IV. TELLURIUM GLANCE, or BLACK TELLURIUM.
1. Prismatic Tellurium Glance.
Genus V. MOLYBDENA, or MOLYBDENA GLANCE.
1. Rhomboidal Molybdena.
* Molybdena Ochre.
Genus VI. BISMUTH GLANCE.
1. Prismatic Bismuth-Glance.
* Bismuth Ochre.
** Aicular Bismuth-Glance, or Needle Ore.
Genus VII. ANTIMONY GLANCE.
1. Prismatic Antimony-Glance.
2. Prismatoidal Antimony-Glance, or Grey Antimony.
3. Axotomous Antimony-Glance, or Bournonite.
- 1. Diprismatic Melane-Glance, Black Antimony-Ore of Werner.
- 2. Prismatic Melane-Glance, Brittle Silver-Glance of Werner.
- 1. Prismatic Manganese-Blende.
- 1. Dodecahedral Zinc-Blende.
- 1. Prismatic Antimony-Blende, or Red Antimony.
- 1. Rhomboidal Ruby-Blende, or Red Silver.
- 2. Peritomous Ruby-Blende, or Cinabar.
- 1. Prismatoidal Sulphur, or Yellow Orpiment.
- 2. Hemi-Prismatic Sulphur, or Red Orpiment.
- 3. Prismatic Sulphur, or Common Sulphur.
- 1. Pyramidal Mellilite, or Honey-Stone.
- 1. Yellow Mineral Resin, or Amber.
- 2. Fossil Copal.
- 3. Black Mineral Resin.
- 4. Retinite.
- 5. Dysodilite.
- 1. Bituminous Mineral-Coal.
- 2. Glance-Coal.
- 1. Allophane.—2. Bismuthic Silver.—3. Bloedite.—4. Fluat of Cerium.—5. Conite.—6. Cronstedtite.—7. Couzeranite.—8. Gieseckite.—9. Gismondite.—10. Hisengerite.—11. Humite.—12. Ligurite.—13. Mellilite.—14. Molybdenic Silver.—15. Orthite.—16. Polyhalite.—17. Pyralolite.—18. Pyrothite.—19. Pyrosmalite.—20. Sapparite.—21. Skorodite.—22. Spinellane.—23. Stilpnosiderite.—24. Sordawalite.—25. Wavellite.—26. Yttrocerite.—27. Zurlite.
Mode of determining a Mineral, or of referring it to its place in the System.
The characters principally employed in the formation of what is called the Specific Character are the regular crystallizations (including cleavage); the de-
grees of hardness; and the specific gravity. The first Mineralogy character then given in the Specific Character is the system of crystallization to which the form and cleavage of the species belongs. Then follows, together with its dimensions (if known), the fundamental form, from which all other simple and compound forms are derived. In rhomboids, that edge which ends in the apex of the axis, that is to say, the terminal edge is given; for instance, in calcareous spar, ; in isosceles four-sided pyramids, both edges, first the terminal one, and then that on the base, are mentioned; for instance, in pyramidal zircon, , ; and in scalene four-sided pyramids, first, both of the terminal edges, and then that at the basis, are given: thus, in prismatic topaz, , , . In this system, besides the dimension of the finite forms, those of the infinite ones, or of the limits, are mentioned, as in the last example, , and so on; which is very convenient, as the cases in which these can be examined occur more frequently than those in which the edges of pyramids can be measured.
After this follows the indication of the general aspect of the combinations, explained in the foregoing §§ 63-67, under the denominations of rhomboidal, hemi-prismatic, &c. Of the former are mentioned the angles at the edges of combination, of the latter that terminal edge, which is formed by the intersection of the remaining faces of the scalene four-sided pyramid.
With respect to cleavage, the expression "cleavage, ," for instance in rhomboidal calcareous spar, means, that this mineral has its cleavage parallel to the faces of a rhomboid, similar to the fundamental form of the species; "cleavage , , " in pyramidal garnet means that this mineral has its cleavage parallel to the faces of two rectangular prisms, and at the same time perpendicular to their axis; "cleavage " in prismatic chrysolite, indicates that the cleavage of this mineral passes at the same time through the axis and the short diagonal of the prism ; and "cleavage , , ," expresses, for instance, in paratomoous augite, that the individuals of this species can be cleaved, first parallel to the faces of an obliquangular four-sided prism, of the given dimensions; and, secondly, parallel to planes, which pass through the axis and both diagonals of the prism ; or, what comes to the same, parallel to the faces of a rectangular prism.
If two or more characters, the one of which excludes the other, be coexistent in the character of an order, or of a genus, as in the genus Corundum, "Tessular, rhomboidal, prismatic," the meaning is, that an individual belonging to this genus must be either tessular, or rhomboidal, or prismatic; because only one of these three can take place at the same time. In the specific character this never happens, because all the forms must belong to one system.
If a mineral is to be determined, first its form must be made out, at least so far as to know the system to which it belongs. Then hardness and specific gravity must be tried with proper accuracy, and expressed in numbers. It is sufficient, however, to know the latter to one or two decimals. The specific character requires these data; and they are also of use in the characters of the genera, orders, and classes. This being done, the system may be consulted, and this will at the same time point out what other characters are wanting; so that a mere inspection of the mineral, or a very easy experiment, for instance, to try the streak upon a file, or, still better, upon a plate of porcelain biscuit, will be sufficient. Having advanced in this manner to the character of the species, it will, in some instances, be necessary, and in all cases advisable, for the sake of certainty, to have recourse to the dimensions of the forms. This is particularly necessary, if the genus to which the mineral belongs contains several species having forms of the same system, as is the case in the genus Augite. This determination of the dimensions of the forms may be effected by the common goniometer, the differences in the angles being in general so great, that they cannot easily be missed, even by the application of this instrument.
It will seldom be necessary to read over the whole of any character of a class, order, genus, or species, excepting those which comprise the individual; one character that does not agree sufficing for its exclusion. Thus even the characters of the orders, though the longest, will not be found troublesome.
The application of the method will become very easy and expeditious, by taking particular notice of some characters, which may be termed prominent. Such are a metallic aspect; a high degree of specific gravity (particularly if the mineral is not metallic), and a high degree of hardness. The observation of these will immediately decide whether an individual can belong to any particular class, order, genus, or species. It is understood, that if it be not thereby excluded, the other characters must next be examined, till either an excluding one be found, or, if not, the individual may be considered as belonging to that class, order, &c. with which it has been compared and found to agree.
Example.—In illustration of this, let us take the following example: Let the form of an unknown mineral be a combination of a scalene eight-sided pyramid, of an isosceles four-sided pyramid, and of a rectangular four-sided prism; the cleavage parallel to the faces of two rectangular four-sided prisms, in a diagonal position to each other; form and cleavage, therefore, pyramidal, or belonging to the pyramidal system. Let hardness be ; specific gravity .
In this case, both hardness and specific gravity are prominent characters, and exclude at once the individual from the first and third, but not from the second class; with the characters of which its other properties also perfectly agree. Hence the individual belongs to the second class.
Comparing the properties of the individual with
the characters of the orders in the second class, hardness and specific gravity will be found too great for the order Haloide; hardness too great for the orders Baryte and Kerate; both of them too great for the orders Malachite and Mica; and specific gravity too great for the orders Spar and Gem. But in the character of the order ore, both hardness and specific gravity fall between the fixed limits, and cannot exclude the individual from this order. The other parts of this character are now to be taken in consideration. If the lustre of the individual be metallic, its colour must be black, otherwise it cannot belong to the order ore. But the lustre is not metallic; therefore the colour of the individual is of no consequence; that is, this conditional part of the character does not affect the individual, and consequently cannot determine its place. Since the lustre is not metallic, the individual must exhibit adamantine, or imperfect metallic lustre: the first will be found particularly in the fracture. The next part of the character refers to minerals of a red, yellow, brown, or black streak; and as the individual gives none of these, its streak being white, this part of the character does not come into consideration. Hardness keeps between the limits, as stated in the character of the order ore. Should it be and less, the streak must be yellow, red, or black; but hardness is , therefore the colour of the streak is indifferent. If the hardness be and more, and streak white, then the specific gravity must be and more. Now, this condition takes place: hardness is , and the streak is white; the specific gravity being , which is greater than . Lastly, the specific gravity keeps within the limits.
As far as respects the individual which is to be determined, all the characters in the characteristic of the order ore may be divided into two parts. The first part contains those which refer to the individual; the second those which do not; the last afford no decisive distinctions. But with the first all the properties of the mineral agree. These properties agree consequently with the whole character of the order, as far as it is applicable to the individual, and determine it to belong to the order ore; or, in shorter terms, to be an ore.
Beginners may also compare the characters of the remaining orders. Sometimes they find one individual belonging to two orders, in which case there must be evidently a mistake in the comparison, which would perhaps not have been discovered, had they stopped at the first order, which does not exclude it. In the present case, the want of metallic lustre excludes the individual from the orders, metal, pyrites, and glance; hardness from the order blende; and both hardness and specific gravity from the order sulphur. The individual can, therefore, be nothing else than an ore; and the characters of the genera of the order Ore may now be examined.
If we consider again hardness and specific gravity as prominent, the individual will be immediately excluded from the genera titanium-ore, zinc-ore, and copper-ore, but not from the genus tin-ore. The form of the pyramidal system, and the white streak, show that it belongs to this genus. From the genus scheelium-ore, it is excluded by its
Mineralogy. too great hardness, and too low specific gravity. From the genera tantalum, uranium, cerium, chrome, iron, and manganese-ore, by hardness and specific gravity, both of them being too high; as also by its white streak, which only agrees with that genus from which the individual differs most by its hardness and specific gravity. The form also does not agree with any in these genera, consequently the individual can belong to no other than to the genus tin-ore.
This genus contains but one species. The conclusion that the individual must belong to this species might, nevertheless, be erroneous. There could exist a second species of this genus. The dimensions of the form must now be accurately considered. If these coincide with the angles given in the character, the highest degree of certainty that the individual belongs to or is pyramidal tin-ore, will be obtained.
Perfect determination supposes all the Characters to be known.
The perfect determination of an individual depends, as the above example has shown, upon the possibility of making out correctly those three properties, viz. form, including cleavage, hardness, and specific gravity. In botany it is the same. The characters must be observable, otherwise the determination will be impossible. In mineralogy, the method affords sometimes more: it leads to a correct determination, even if the knowledge of the form remains imperfect. But it will be an useful rule for beginners to occupy themselves at first with the determination of such individuals as present properties which can be easily and fully investigated. The rest will come of itself, when their knowledge of the mineral kingdom, and particularly of the properties of minerals, increases, and when they have by experience acquired the skill to judge properly of form and cleavage, at least, so far as is necessary for the determination of the system of crystallization, even in those cases where form and cleavage are somewhat difficult to be observed. This exercise is recommendable to every naturalist who intends to acquire a satisfactory knowledge of minerals, by means of the present method.
Immediate and Mediate Determination.
The method of determination, illustrated by an example at page 432, is termed the immediate determination, because it is applied immediately to the individual which is to be determined. The contrary of this is the mediate determination, so called on account of its mediate application to the given individual. That variety of hemiprismatic augite, which is known by the name amianthus, occurs in crystals so very seldom, as to withdraw their form, supposing it to be regular, from the sight, aided even by the most powerful magnifying instruments; cleavage is evidently still less observable. These crystals are flexible like fibres of flax, their hardness, therefore, cannot be estimated. Their surface has so great an extent in respect to their bulk, that they will swim in water, though endowed with a pretty considerable specific gravity, which, therefore, cannot
be ascertained. Some varieties, however, may be observed, whose crystals are a little thicker, though, in other respects, these varieties perfectly agree with amianthus. These varieties lose their flexibility, yet they are too frangible to be able to sustain the trial of hardness. Others are still thicker, but the dimensions of their forms cannot be ascertained on account of their minuteness. They sink in water, and scratch prismatic gypsum, but they break, if tried upon calcareous spar. By thus proceeding, we come to such varieties, as possessing a discernible form, allow the cleavage to be investigated; we find their specific gravity about three times that of the water, and their hardness between five and six. These will be immediately determinable, and be found to belong to the species of hemiprismatic augite. Chalk, rock-milk, clay-slate, and a great many other minerals not allowing of an immediate determination, are determined in the same way, and thus nothing escapes in the natural history method, which in any one of the other methods can be an object of determination.—Vide Edinburgh Philosophical Journal, for fuller details in regard to the determination of species, and also for a series of observations on the principles of the Natural History method.
NATURAL HISTORY OF SIMPLE MINERALS.
CLASS I.
Specific gravity under 3.8. If solid, is sapid. No bituminous smell.
Order I.—GAS.
Sp. gr. = 0.0001, — 0.00014. Elastic. Not acid.
Genus I.—HYDROGEN GAS.
Evident smell. Sp. gr. = 0.0001, — 0.00014.
1. Pure Hydrogen Gas.
Specific Character.—Hydrogenous smell. Sp. gr. = 0.00012.
Geognostic and Geographic Situations.—Emanates from rocks of limestone, and of the coal formation, not only in Europe, but in other quarters of the globe.
2. Empyreumatic or Carburetted Hydrogen Gas.
Specific Character.—Empyreumatic smell. Sp. gr. = 0.0008.
Geognostic and Geographic Situations.—Rises from marshes in different parts of Great Britain, and from marshes and volcanoes in other countries.
3. Sulphuretted Hydrogen Gas.
Specific Character.—Smell of putrid eggs. Taste nauseous and bitter. Sp. gr. = 0.00135.
Geognostic and Geographic Situations.—Rises from marshes, sulphureous springs, and volcanoes. It is met with in many places in Great Britain.
4. Phosphuretted Hydrogen Gas.
Specific Character.—Smell of putrid fish. Sp. gr. unknown.
Mineralogy. Geognostic and Geographic Situations.—It rises from marshy places, where organic substances are in a state of decomposition.
Genus II.—ATMOSPHERIC AIR.
Without smell or taste. Sp. gr. = 0.001, — 0.0015.
1. Pure Atmospheric Air.
Specific Character.—Without smell or taste. Forms the atmosphere which surrounds the earth.
Order II.—WATER.
Liquid. Tasteless, or with sensible taste and smell. Sp. gr. = 1.1, — 1.0269.
Genus I.—ATMOSPHERIC WATER.
Without smell or taste.
1. Pure Atmospheric Water.
Specific Character.—Without smell or taste. This is common rain, river, and spring water. Mineral waters might be introduced into this part of the system.
Genus II.—SEA WATER.
Sensible smell and taste.
1. Common Sea Water.
Specific Character.—Bitter nauseous taste, and disagreeable smell. Is the water of the ocean.
Order III.—ACID.
Sp. gr. = 0.0045, — 3.7. Acid.
Genus I.—CARBONIC ACID.
Taste slightly acid. Sp. gr. = 0.0018.
1. Aeriform Carbonic Acid.
Specific Character.—Elastic. Taste acidulous and pungent.
Geognostic and Geographic Situations.—Occurs in marshy places and in acidulous waters, in Great Britain and other countries.
Genus II.—MURIATIC ACID.
Smell of saffron, and strong acid taste. Sp. gr. = 0.0023.
1. Aeriform Muriatic Acid.
Specific Character.—Elastic. Smell pungent and suffocating.
Geognostic Situation.—Rises from volcanoes.
Genus III.—SULPHURIC ACID.
If gaseous, the smell is sulphureous. If liquid, the taste is strongly acid. Sp. gr. = 0.0025, — 1.5.
1. Aeriform Sulphuric Acid.
Specific Character.—Elastic. Sp. gr. = 0.0028.
Geognostic Situation.—Often rises in considerable quantities from volcanoes.
2. Liquid Sulphuric Acid.
Specific Character.—Liquid. Sp. gr. = 1.4, — 1.5.
Genus IV.—BORACID ACID.
Solid. Sp. gr. under 3.0.
1. Prismatic Boracic Acid.
Specific Character.—Prismatic. Pyramid unknown. Occurs in scaly crusts. Taste first sourish, or sub-acid, then bitter and cooling, and lastly, sweetish.
Geognostic and Geographic Situations.—Found on the edges of hot springs in Italy, &c.
Genus V.—ARSENIC ACID.
Solid. Sp. gr. above 3.0.
1. Octahedral Arsenic Acid.
Arsenic oxyde.—Hauy.
Specific Character.—Tessular. Cleavage, octahedral. Taste sweetish-astringent. Hardness unknown. Sp. gr. = 3.6, — 3.7.
Description.—Colour white. Occurs in delicate capillary crystals; also massive, in crusts, stalactitic, reniform and betryodal. Translucent or opaque.
Geognostic and Geographic Situations.—Occurs in veins at Andreasberg in the Hartz.
Order IV.—SALT.
Sp. gr. = 1.2, — 2.9. Solid. Not acid.
Genus I.—NATRON.
Prismatic. Taste, pungent and alkaline. Hardness, = 1.0, — 1.5. Sp. gr. = 1.5, — 1.6.
1. Prismatic Natron.—Jameson.
Prismatisches Natron-Salz, Mohs.—Natürliches Mineral-Alkali, Werner.—Soude carbonatée, Hauy.
Specific Character.—Prismatic. Pyramid unknown. Combination, hemi-prismatic. Cleavage prismatic.
Description.—Its chief colours are grey, white, and yellow. Occurs in acicular crystals, in radiated and granular distinct concretions; also in loose earthy particles, and in crusts. Is more or less translucent.
Geognostic and Geographic Situations.—Occurs in crusts on rocks and soils of different kinds; and also in the waters of natron lakes and springs. It is particularly abundant in the natron lakes in Egypt.
Genus II.—GLAUBER SALT.
Prismatic. Taste, first cooling, then saline and bitter. Hardness, = 1.5, — 2.0. Sp. gr. 1.4, — 1.5.
1. Prismatic Glauber Salt.—Jameson.
Prismatisches Glauber Salz, Mohs.—Natürliches Glauber Salz, Werner. Soude sulphatée, Hauy.
Specific Character.—Prismatic. Pyramid unknown.
Combination, hemi-prismatic. . Cleavage, .
perfect. Less perfect, . (Fig. 29, 28.)
Description.—Colour white, sometimes inclining to yellow. Occurs in acicular crystals, granular con-
Mineralogy. cretaceous, stalactitic, in loose earthy particles, and in crusts. More or less translucent.
Geognostic and Geographic Situations.—Occurs on soils and rocks of different descriptions, in Scotland, England, and other countries.
Genus III.—NITRE.
Prismatic. Taste, cooling and saline. Hardness, =2.0. Sp. gr. 1.9, —2.0.
1. Prismatic Nitre.—Jameson.
Prismatisches Nitrum-Salz, Mohs. — Natürlicher Salpeter, Werner. — Potasse nitratée, Haüy.
Specific Character.—Prismatic. Pyramid = ; ; . Cleavage, .
More distinct, . (Fig. 30, 29.)
Description.—Colour white, grey, and sometimes yellow. Occurs in acicular crystals, in crusts, and in fibrous concretions. More or less translucent.
Geognostic and Geographic Situations.—Occurs in crusts of limestone, marl, sandstone, calc-tuff, chalk, and on soils of particular kinds; also in crusts of the walls of limestone caves. Occurs in considerable abundance in limestone caves in Italy, in caves of various descriptions in America, and in abundance on the surface of the ground in many of the Tartarian plains.
Genus IV.—ROCK-SALT.
Tessular. Taste, saline. Hardness =2.0. Sp. gr. =2.2, —2.3.
1. Hexahedral Rock-Salt.—Jameson.
Hexaedrisches Steinsalz, Mohs.
Specific Character.—Tessular. Cleavage, hexahedral.
Description.—Most frequent colours grey and white; sometimes also blue, red, yellow, and green. Occurs in granular, fibrous, radiated, and prismatic concretions; massive, dentiform, and stalactitic. Lustre between vitreous and resinous. More or less transparent and translucent.
Geognostic and Geographic Situations.—It occurs in beds, imbedded masses, and veins, associated with saliniferous clay, gypsum, limestone, sandstone, and anhydrite, in the salt formation; also, in layers and crusts on soils of particular kinds, and deposited on the shores of salt lakes, and in the vicinity of salt springs. Occurs abundantly in Cheshire, and also in other parts of England.
Genus V.—SAL AMMONIAC.
Tessular. Taste, pungent and urinous. Hardness =1.5, —2.0. Sp. gr. 1.5, —1.6.
1. Octahedral Sal Ammoniac.—Jameson.
Octaedrisches Salmiac, Mohs. — Natürlicher Salmiac, Werner. — Ammoniaque muriatée, Haüy.
Specific Character.—Tessular. Cleavage, octahedral.
Description.—Colours white, grey, yellow, and sometimes green and bluish. Occurs in granular and fibrous concretions; also in efflorescences, in crusts, stalactitic, botryoidal, tuberose, and corroded. More or less translucent.
Geognostic and Geographic Situations.—Occurs in Mineralogy. crusts in the fissures and on the surfaces of volcanic rocks, as in Vesuvius, Ætna, &c.
Genus VI.—VITRIOL.
Pyramidal, prismatic. Taste, astringent. Hardness =2.0, —2.5. Sp. gr. =1.9, —2.3.
1. Hemi-prismatic Vitriol, or Green Vitriol.—Jameson.
Hemiprismatisches Vitriol-Salz, Mohs. — Eisen Vitriol, Werner. — Fer Sulfatée, Haüy.
Specific Character.—Prismatic. Pyramid = ; ; , . Combination, hemi-prismatic . Cleavage, .
More perfect, . (Fig. 40.) The inclination of to . Green. Hardness, =2.0. Sp. gr. =1.9, —2.0.
Description.—Colour green. Occurs regularly crystallized, in fibrous concretions, massive, stalactitic, botryoidal, and reniform. More or less translucent and transparent.
Geognostic and Geographic Situations.—Occurs in coal and iron mines, both in Scotland and England.
2. Prismatic Vitriol, or Blue Vitriol.—Jameson.
Prismatisches Vitriol-Salz, Mohs. — Kupfervitriol, Werner. — Cuivre Sulfatée, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Combination, tetartoprismatic. Cleavage, two faces, one more distinct than the other; incidence, . Hardness =2.5. Sp. gr. =2.2, —2.3.
Description.—Colour blue. Occurs distinctly crystallized, massive, stalactitic, and dentiform. More or less transparent and translucent.
Geognostic and Geographic Situations.—Occurs in copper mines in England and Ireland.
3. Pyramidal Vitriol, or White Vitriol.—Jameson.
Pyramidales Vitriol-Salz, Mohs. — Zink-vitriol, Werner. — Zinc sulfatée, Haüy.
Specific Character.—Pyramidal. Pyramid = ; . Cleavage unknown, and imperfect. White. Hardness unknown. Sp. gr. =2.0.
Geognostic and Geographic Situations.—Occurs in mines where blende is met with, both in Flintshire and Cornwall.
Genus VII.—EPSOM SALT.
Prismatic. Taste bitter and saline. Hardness unknown. Sp. gr. unknown.
1. Prismatic Epsom Salt.—Jameson.
Bittersalz, Mohs. — Natürlicher Bittersalz, Werner. — Magnésie Sulfatée, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage very imperfect prismatoidal.
Description.—Colours white and grey. Occurs in crusts, botryoidal, reniform, and crystallized, —varies from transparent to translucent.
Geognostic and Geographic Situations.—Occurs along with natural alum at Hurlet near Paisley.
Genus VIII.—ALUM.
Tessular. Taste sweetish, astringent, and acidulous. Hardness = 2.0, 2.5. Sp. gr. = 1.7, 1.8.
1. Octahedral Alum.—Jameson.
Octaedrisches Alaun, Mohs.—Natürlicher Alaun, Werner.
Specific Character.—Tessular. Cleavage octahedral.
Description.—Colours white. Occurs in farinaceous efflorescences, stalactitic, and in fibrous concretions, more or less translucent.
Geognostic and Geographic Situations.—Generally occurs incrusting aluminous minerals, and in this situation it is met with in various parts of Scotland and England.
Genus IX.—BORAX.
Borax-Salz, Mohs.
Prismatic. Taste feebly sweetish and alkaline. Hardness = 2.0, 2.5. Sp. gr. = 1.5, 1.7.
1. Prismatic Borax.—Jameson.
Prismatisches Borax-Salz, Mohs.—Soude Boratée, Hauy.
Specific Character.—Prismatic. Combination, hemiprismatic, Cleavage More distinct (Fig. 32, 29.)
Description.—Colours white, grey, and green. Occurs crystallized, internally shining and resinous. Fracture, flat, conchoidal. Semitransparent.
Geognostic and Geographic Situations.—Occurs in the soil, and in the water of springs, in Thibet and Persia.
Genus X.—GLAUBERITE.
Brithyn-Salz, Mohs.
Prismatic. Taste feebly saline and astringent. Hardness = 2.5, 3.0. Sp. gr. = 2.7, 2.9.
1. Prismatic Glauberite.—Jameson.
Prismatisches Brithyn-Salz, Mohs.—Glauberite, Hauy.
Specific Character.—Prismatic. Pyramid unknown. Combination hemiprismatic. Cleavage , perfect.
Indistinct (Fig. 35, 30.)
Description.—Colours white and yellow. Occurs crystallized in oblique four-sided prisms. Shining lustre. Fracture conchoidal. Transparent. Brittle.
Geognostic and Geographic Situations.—Occurs in masses of rock-salt, associated with clay, at Villarubia near Ocanas, in the province of Toledo, in Spain.
CLASS II.
Specific gravity above 1.8. Inviscid.
Order I.—HALOIDE.*
No metallic lustre. Streak white or grey. Hardness = 1.5, 5.0. Sp. gr. = 2.2, 3.3.
If pyramidal, or prismatic, the hardness = 4.0, and less. If tessular, the hardness = 4.0. If single highly perfect faces of cleavage, the Sp. gr. = 2.4, and less. If the hardness is under 2.5, the Sp. gr. = 2.4, and less. If the Sp. gr. = 2.4, and less, the hardness is under 2.5, and no resinous lustre.
Genus I.—GYPSUM.
Prismatic. Hardness = 1.5, 3.5. Sp. gr. = 2.2, 3.0.
If the Sp. gr. is above 2.5, there are cleavages in three directions, perpendicular to each other, and two are more distinct than the others.
1. Prismatoidal Gypsum, or Common Gypsum.—Jameson.
Prismatoidisches Gyps-Haloid, Mohs.—Chaux sulfate, Hauy.
Specific Character.—Prismatic. Pyramid = Combination. Hemiprismatic, Cleavage,
, very perfect and distinct, (inclination to each other, = ) (Fig. 41.) Hardness = 1.5, 2.0. Sp. gr. = 2.2, 2.4.
Description.—Most frequent colours white and grey; occurs also yellow, red, blue, green, brown, and even black. Occurs in regular crystals; in granular, scaly-granular, and fibrous distinct concretions; massive, disseminated, and dentiform. Lustre alternates from splendid to glimmering, and is pearly. Fracture splintery. Fragments indeterminate angular and blunt-edged. Alternates from transparent to translucent on the edges.
The transparent and highly crystallized varieties are named selenite; those in granular concretions, foliated granular gypsum; those disposed in fibrous concretion, fibrous gypsum; the splintery fracture characterizes the compact gypsum; while those varieties composed of scaly-granular concretions form the subspecies named scaly-foliated gypsum. Some varieties, composed of fine scaly or dusty and slightly cohering particles, are named earthy gypsum.
Geognostic and Geographic Situations.—Selenite, the purest subspecies, occurs most frequently in what are called the gypsum and salt formations of the secondary class of rocks; also in metalliferous veins of different descriptions, and in various alluvial clays and marls. The foliated granular subspecies occurs in beds, in transition, and secondary rocks, being in the former intermixed with mica, in the latter with quartz, boracite, &c. The compact variety
* From "αλς, salt; and "ιδος, the appearance (habitus).
Mineralogy occurs in considerable abundance along with the granular in the secondary gypsum formation, and the fibrous is disposed in veins, in the same formation, which also contains the scaly foliated and the earthy kinds.
The salt mines in England afford examples of nearly all the subspecies, and several of them are also met with in Scotland.
2. Prismatic Gypsum, or Anhydrite.—Jameson.
Prismatisches Gyps-Haloide, Mohs.—Muriacit, Werner.—Chaux Anhydro-Sulphatée, Hauy.
Specific Character.—Prismatic, Pyramid = ; ; . Cleavage, . . Less perfect . Traces of . (Fig. 29, 28, 27, 30.) Hardness = 3.0, —3.5. Sp. gr. = 2.7, —3.0.
Description.—Colours white, blue, red, and grey. Occurs crystallized; in granular, fibrous, and lamellar concretions; massive, and vermicularly convoluted or contorted. Lustre alternates from splendid to glistening, and is pearly. Fracture splintery and conchoidal. Alternates from transparent to translucent on the edges.
Geognostic and Geographic Situations.—Occurs massive, and in beds in the salt and secondary gypsum formations. Is frequently intermixed with rock salt, also with stinkstone, saliniferous clay, and occasionally with ores of different kinds. Some varieties are met with in transition and primitive rocks. Several of the varieties are found in the red sandstones of England and Scotland.
Genus II.—CRYOLITE.
Prismatic. Cleavage in three directions, perpendicular to each other, of which one is more perfect than the others. Hardness = 2.5, —3.0. Sp. gr. = 2.9, —3.0.
1. Prismatic Cryolite.—Jameson.
Kryolite, Werner.—Prismatisches Kryon-Haloide, Mohs.—Alumine fluatée alcaline, Hauy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, . Less distinct, . . Traces of . (Fig. 27, 29, 28.)
Description.—Colours white, brown, and red. Occurs massive, disseminated, and in lamellar concretions. Internally shining, and lustre vitreous, inclining to pearly. Fracture uneven. Fragments cubical. Translucent. Brittle, and easily frangible.
Geognostic and Geographic Situations.—It has hitherto been found only in West Greenland, where it occurs in gneiss, and associated with iron pyrites and galena or lead-glaucite.
Genus III.—ALUMSTONE.
Alaun Haloide, Mohs.—Alaunstein, Werner. Rhomboidal. Hardness = 5.0. Sp. gr. = 2.4, —2.6.
1. Rhomboidal Alumstone.—Jameson.
Rhomboidrisches Alaun Haloide, Mohs.
Specific Character.—Rhomboidal. Rhomboid unknown. Cleavage . .
Description.—Colours white, red, and rarely grey. Occurs massive, porous, and vesicular. Lustre feebly glimmering. Fracture uneven. Feebly translucent on the edges. Brittle, and easily frangible.
Geognostic and Geographic Situations.—Occurs in beds and large irregular masses in porphyry in Hungary, and in veins and drusy cavities in aluminous rocks at Tolfa, near to Civita Vecchia.
Genus IV.—FLUOR.
Tessular. Hardness = 4.0. Sp. gr. = 3.0, —3.3.
1. Octahedral Fluor.—Jameson.
Octaedrisches Flus-Haloide, Mohs.—Chaux fluatée, Hauy.
Specific Character.—Tessular. Cleavage Octahedral.
Description.—Colours white, grey, black, blue, green, yellow, red, and brown. Occurs regularly crystallized, in granular, prismatic, and lamellar concretions, massive, and disseminated. Lustre from splendid to feebly glimmering, and vitreous. Fracture even, inclining to splintery and to conchoidal. More or less transparent and translucent. Brittle, and easily frangible.
The varieties, with even fracture and feeble lustre, are named compact fluor; those in which the cleavage is distinct are named common or foliated fluor; and some rare, dull, earthy, and loosely aggregated varieties, which occur, incrusting other minerals, are described under the name earthy fluor.
Geognostic and Geographic Situations.—It occurs in veins and beds in primitive gneiss, mica slate, and clay slate, in various remarkable metalliferous formations of cobalt, silver, tin, lead, copper, &c.; less frequently in transition rocks, and very abundantly in some secondary rocks, as limestone, and rarely in secondary porphyries. It is a rare mineral in Scotland, its principal localities being Monaltree, in Aberdeenshire, Banffshire, Papa Stour, in Shetland, and Gourock, in Renfrewshire. It is very abundant in several of the mining districts in England.
Genus V.—APATITE.
Rhomboidal. Hardness = 5.0. Sp. gr. = 3.0, 3.3.
1. Rhomboidal Apatite.
Rhomboidrisches Flus-haloide, Mohs.—Apatit, Werner.—Chaux phosphatée, Hauy.
Specific Character.—Rhomboidal. . Combination, di-rhomboidal. ; , hemi-dirhomboidal, with parallel planes. Cleavage, . . . Sp. gr. = 3.0, —3.3.
Description.—Colours white, green, blue, red, yellow, and brown. Occurs regularly crystallized; in concretions which are granular, lamellar, and fibrous; massive and disseminated; lustre resinous, and varying from splendid to glimmering. Fracture conchoidal and uneven. Alternates from transparent to feebly translucent on the edges. Brittle, and easily frangible.
One set of varieties, in which the cleavage is very distinct, is named foliated apatite; another, in which
Mineralogy. the fracture is conchoidal, is named conchoidal aptite; and the varieties in which the fracture is uneven are named phosphorite.
Geognostic and Geographic Situations.—Occurs in gneiss, near Kincardine, in Ross-shire; in the same rock in the Shetland Islands; and in veins in greenstone, in the Island of Rume. Several varieties are met with in Cornwall.
Genus VI.—LIMESTONE.
Kalk-Haloide.—Mohs.
Rhomboidal, prismatic. Cleavage, rhomboido-paratomous, prismatoidal. Hardness = 3.0, —4.5. Sp. gr. = 2.5, —3.2. If the hardness is above 4.0, the specific gravity = 2.8 and more.
1. Prismatic Limestone, or Arragonite.—Jameson.
Prismatisches Kalk-Haloide, Mohs.—Arragon, Werner.
Specific Character.—Prismatic. Pyramid = ; ; . . Cleavage, . . More distinct . Fig. 42. Hardness = 3.5, —4.0. Sp. gr. = 2.6, —3.0.
Description.—Colours white, grey, green, and violet-blue. Occurs regularly crystallized; also in prismatic concretions and massive. Lustre vitreous, inclining to resinous, and shining and glistening. Fracture conchoidal, passing into uneven. Translucent and transparent. Brittle, and easily frangible.
Geognostic and Geographic Situations.—Occurs along with galena in the lead-mines of Leadhills, and in secondary trap-rocks in different parts of Scotland.
2. Rhomboidal Limestone.—Jameson.
Rhomboedrisches Kalk-Haloide, Mohs.—Chaux carbonatée, Hauy.—Kalk-spath, Werner.
Specific Character.—Rhomboidal. Rhomboid = . Cleavage, R. Hardness = 3.0. Sp. gr. = 2.5, —2.8.
Description.—Colours very varied, but of all the tints, white and grey are the most frequent; besides these, the following kinds also occur, viz. red, blue, green, yellow, brown, and rarely black. Occurs regularly crystallized, and of all known minerals, exhibits the greatest number of varieties of the rhomboidal series of crystallization; also in granular, prismatic, tabular, and globular distinct concretions. Its other forms are massive, disseminated, globular, botryoidal, reniform, tuberose, stalactitic, tubular, claviform, coralloidal, cellular, and curtain-shaped. Its lustre varies from splendid to dull, and is vitreous, inclining sometimes to pearly, sometimes to resinous. Fracture splintery, conchoidal, earthy, and uneven. Alternates from transparent to opaque. Generally brittle, and easily frangible.
Those varieties which are regularly crystallized, and possess high degrees of transparency, are named calcareous-spar; those in angulo-granular distinct concretions, with a lower lustre and transparency than the former, are the foliated granular limestone, or crystalline marble of authors; the varieties with
splintery or conchoidal fractures are named compact limestone; other varieties having a grey or brown colour, dull earthy fracture, and which, on rubbing, give out a sulphureo-bituminous smell, are named stinkstone; the black varieties in granular and prismatic concretions, or with a compact fracture, with a glimmering or shining lustre, and low degree of translucency on the edges or complete opacity, and which, on rubbing, yield a sulphureo-bituminous odour, are named anthraconite; those limestones which have the oolitic structure, or are composed of spherical granular concretions, set on a marly basis, are named roestone or oolite; the soft varieties with earthy fracture and white colour are named chalk; the varieties with dull fracture surface, in loosely cohering pieces and crusts, and so light as nearly to swim upon water, are named agaric mineral; the fibrous varieties are named common fibrous limestone or satin-spar, and fibrous calc-sinter, or calcareous alabaster; the earthy looking opaque varieties that occur in many particular external shapes, near calcareous springs, and on the borders of lakes, are named calc-tuff; while the varieties in spherical round granular concretions, and concentric lamellar concretions, found near hot springs, are named pea-stone; the slate-spar of mineralogists is a variety in lamellar concretions, with a beautiful pearly lustre and feeble translucency; varieties with earthy fracture, more or less inclined to splintery and conchoidal, are named marl; and, lastly, the opaque dull black varieties, with slaty fracture, are named bituminous marl-slate.
Geognostic Situation.—This mineral is one of the most abundant and widely distributed with which we are acquainted. Calcareous spar, one of its principal kinds, occurs in every rock from granite to the newest member of the secondary series. It generally occurs in veins with numerous metalliferous minerals, and assists in an eminent degree in characterizing the vast host of mineral veins in primitive, transition, and secondary rocks. In the state of granular, foliated, and compact limestones, also in the form of oolite, chalk, and Lucullite, it forms beds, hills, mountains, and even ranges of mountains. The beautiful fibrous limestone or satin spar occurs in veins in clay slate, and in rocks of the coal formation, while all the beautiful forms of calc-sinter are met with ornamenting the walls and floors of caverns in limestone and other formations; calc tuff abounds around cold, and also warm springs, frequently incrusting organic bodies, forming the calcareous incrustations so well known to mineralogists. Pea-stone is also a production of warm springs. The white, porous, and nearly supernatant mineral agaric incrusts rocky cliffs, particularly in limestone hills, and the rare variety, named slate spar, has hitherto been found only in primitive limestone.
Geographic Situation.—England and Scotland abound in interesting varieties of calcareous spar, and the mountains, hills, and valleys of Great Britain afford numerous localities of many of the different kinds of marble, limestone, chalk, marl, Lucullite, and oolite, while its calcareous springs, and caves and caverns, exhibit numerous deposits of calc tuff and of calc sinter.
Macrotypes Kalk-haloid, Mohs.—Braunspath, Rhombspath-Dolomite, Werner.—Chaux carbonatée ferrifère perlée, Chaux carbonatée magnésifère, Haüy.
Specific Character.—Rhomboidal. Rhomboid . Cleavage, rhomboidal. Hardness = 3.5, —4.0. Sp. gr. = 2.8, —2.95.
Description.—Colours white, grey, brown, red, and green. Occurs crystallized in rhomboids, in granular and prismatic concretions; massive, disseminated, globular, stalactitic, reniform, and with tabular and pyramidal impressions. Lustre varies from shining to glimmering, and is pearly, sometimes inclining to vitreous. Fracture splintery, conchoidal, and slaty. Varies from transparent to translucent on the edges. Brittle, and easily frangible.
The white varieties in small and fine granular concretions, which are sometimes so loosely aggregated, as to separate by the mere pressure of the finger, are the dolomite-marble of mineralogists; the magnesian limestone of England is a dolomite with brown colours; the green varieties are described under the name Miemite, from Miemo in Tuscany, where they were first found; the brown, red, reddish white, and pearl grey varieties, with very distinct pearly lustre, are arranged together, and described under the names brown spar and pearl spar.
Geognostic and Geographic Situations.—The dolomite marble occurs in the island of Iona; the brown dolomite constitutes a secondary limestone formation very abundant in England; the brown spar and pearl spar are not unfrequent in the lead mines of Scotland and England.
Brachytypes Kalk-haloid, Mohs. Rautenspath, Werner. Chaux carbonatée magnésifère, Haüy.
Specific Character.—Rhomboidal. Rhomboid = . Cleavage rhomboidal. Hardness = 4.0, —4.5. Sp. gr. = 3.0, —3.2.
Description.—Colours white, grey, and yellow. Occurs crystallized in rhombs; also massive and disseminated. Lustre splendid and vitreous-pearly. Fracture imperfect conchoidal. More or less translucent. Brittle, and easily frangible.
Geognostic and Geographic Situations.—Occurs imbedded in chlorite slate on the banks of Loch Lomond, and associated with galena, copper pyrites, and blende, near Newton Stewart, in Galloway.
No true metallic lustre. Streak, white and grey, or orange-yellow. Hardness = 2.5, —5.0. Sp. gr. = 3.3, —7.3. If adamantine, or imperfect metallic lustre, the Sp. gr. = 6.0 and more. If the streak is orange-yellow, the Sp. gr. = 6 and more; and the hardness = 3.0 and less. If the Sp. gr. is under 4.0, and the hardness = 5.0, the cleavage is diprismatic.
Rhomboidal. Hardness = 3.5, —4.5. Sp. gr. = 3.6, —3.9.
Brachytoper Parachros Baryte, Mohs.—Spath Eisenstein, Werner.—Fer Oxydé Carbonaté, Haüy.
Specific Character.—Rhomboidal. Rhomboid = 107. Cleavage, rhomboidal.
Description.—Colours yellow, white, brown, and black. Occurs crystallized in rhombs; also in granular concretions, massive and disseminated. Internally, lustre pearly, and varying from shining to glimmering, and even to splendid. Fracture sometimes splintery. Translucent on the edges. Rather brittle, and easily frangible.
Geognostic and Geographic Situations.—Occurs in metalliferous veins, and in common veins, in primitive, transition, and secondary rocks in different parts of Great Britain and Ireland.
Feroxyde carbonatée concretionné.
Colours brownish black, blackish brown, yellow, and grey. Occurs in stellular fibrous concretions, also globular, reniform, and small botryoidal. Lustre shining and resino-pearly. Fracture uneven. Ranges from semitransparent to opaque. Occurs in drusy cavities in secondary trap rocks, along with calcareous spar, aragonite and calcedony, at Steinheim near Hanau, in Germany.
Hardness = 3.5. Sp. gr. = 3.3, —3.6.
Macrotyper Parachros Baryte, Mohs. Rother Braunstein, Werner. Manganese Oxydé Carbonaté, Haüy.
Specific Character.—Rhomboid = . Cleavage, rhomboidal.
Description.—Colours red and brown. Occurs in granular concretions, also in fibrous concretions, which are scopiformly and stellularly arranged, massive, and reniform. Lustre varies from shining to glimmering, and pearly. Fracture splintery. More or less translucent on the edges; in some rare varieties translucent. Brittle, and rather easily frangible.
The varieties with distinct cleavage are named foliated red manganese; those in fibrous concretions, fibrous red manganese; and the splintery varieties, compact red manganese.
Geognostic and Geographic Situations.—Occurs at Kapnic, in Transylvania, and at Catharinenberg, in Siberia.
Rothstein. Manganèse Oxydé Silicifère.
Specific Character.—Colour bright rose-red. Occurs massive and disseminated. Lustre intermediate
* From μακρής, long; and ῥβρος, the type (fundamental form).
† From βραχύς, short, and ῥβρος, the type.
Mineralogy. between pearly and vitreous. Cleavage sometimes visible. Fracture conchoidal or splintery. Translucent on the edges. Hardness = 5.0, — 5.5. Sp. gr. = 3.5, — 3.7.
Geognostic and Geographic Situations.—Occurs in beds of magnetic iron-ore and iron-glaucophane, in gneiss at Langbanshytta, in Wermeland in Sweden.
Genus III.—CALAMINE.
Zinc-Baryt, Mohs.
Rhomboidal. Prismatic. Hardness = 5.0. Sp. gr. = 3.3, — 4.5. If rhomboidal, the Sp. gr. above 4.0.
1. Prismatic Calamine, or Electric Calamine.—Jameson.
Prismatischer Zink-Baryt, Mohs. Zink Oxyde, Hauy.
Specific Character.—Prismatic. Pyramid = ; ; . . Cleavage, . More distinct, . (Fig. 43.) Hardness = 5.0. Sp. gr. = 3.3, — 3.6.
Description.—Most frequent colours white and yellow; also green, grey, yellow, and brown; and with curved striped colour delineations. Occurs regularly crystallized, and in distinct concretions, which are scopiform radiated, and scopiform fibrous, granular, and curved lamellar. Massive, in crusts, stalactitic, reniform, botryoidal, and cellular. Internally alternates from glistening to dull, and lustre pearly, inclining to adamantine. Fracture small and fine-grained uneven. Varies from transparent to opaque.
Geognostic and Geographic Situations.—Occurs in veins of galena, in greywacke, and clay-slate, and in beds, and imbedded masses in secondary limestone. Is found in the lead mines of Wanlockhead, and in the mines of Flintshire and Leicestershire.
2. Rhomboidal Calamine.—Jameson.
Rhomboidischer Zink-baryt, Mohs.—Galmei, Werner.—Zink carbonaté, Hauy.
Specific Character.—Rhomboidal. Rhomboid = (nearly). Cleavage, rhomboidal. Hardness = 5.0. Sp. gr. = 4.2, — 4.5.
Description.—Colours white, grey, green, yellow, and brown. Occurs regularly crystallized, and in distinct concretions, which are radiated, granular, and curved lamellar; massive, corroded, reniform, stalactitic, botryoidal, and cellular. Internally ranges from shining to dull, and is pearly. Fracture uneven, splintery, and flat conchoidal. Ranges from transparent to opaque.
Geognostic and Geographic Situations.—Occurs in beds, veins, nests, filling up or lining hollows, in transition limestone and in secondary limestone. Derbyshire, Somersetshire, Flintshire, and Durham, afford numerous localities of this mineral.
Genus IV.—TUNGSTEN, or SCHEELIUM.
Hardness = 4.0, — 4.5. Sp. gr. = 6.0, — 6.1.
1. Pyramidal Tungsten.—Jameson.
Pyramidal Scheel-Baryt, Mohs.—Schwerstein, Werner.—Scheelin Calcaire, Hauy.
Specific Character.—Pyramidal. Pyramid = ; . Combination hemi-pyramidal with parallel planes. Cleavage, ; . Mineralogy.
Description.—White is the principal colour; but other varieties, as brown and orange-yellow, occasionally occur. Sometimes crystallized, and also in distinct concretions, which are granular, prismatic, and curved lamellar. Occurs massive and disseminated. External lustre shining and splendid; internal lustre shining and resinous. Fracture uneven or conchoidal. More or less translucent, seldom transparent.
Geognostic and Geographic Situations.—Occurs along with tinstone, wolfram, magnetic iron-ore, and brown iron-ore, in primitive rocks, as in Cornwall.
Genus V. BARYTE.
Hardness = 3.0, — 3.5. Sp. gr. 3.6, — 4.6.
1. Pyramido-Prismatic Baryte, or Strontianite.
Pyramido-prismatischer Hal-Baryt, Mohs.—Strontian, Werner.—Strontiane Carbonaté, Hauy.
Specific Character.—Prismatic. Pyramid unknown.
Cleavage, . . (Fig. 46.) Hardness = 3.5. Sp. gr. 3.6, — 3.8.
Description.—Colours green and grey. Occurs regularly crystallized, and in distinct concretions, which are scopiform radiated, and scopiform fibrous. Lustre shining, glistening, and pearly. Fracture uneven. More or less translucent. Brittle, and easily frangible.
Geognostic and Geographic Situations.—Occurs at Strontian in Scotland in veins of lead glance that traverse gneiss.
2. Di-prismatic Baryte or Witherite.—Jameson.
Di-prismatischer Hal-baryt, Mohs.—Witherite, Werner.—Baryte carbonatée, Hauy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, (nearly). . (Fig. 46.) Hardness = 3.0, — 3.5. Sp. gr. = 4.2, — 4.4.
Description.—Colours white, grey, and yellow. Occurs regularly crystallized, and also in distinct concretions, which are radiated and granular. Occurs massive, cellular, globular, botryoidal, reniform, and stalactitic. Lustre shining and resinous. Fracture uneven, inclining to splintery. Translucent. Brittle, and easily frangible.
Geognostic and Geographic Situations.—Occurs in galena veins, that traverse limestone and sandstone, in Cumberland and Durham.
3. Prismatic Baryte, or Heavy-Spar.—Jameson.
Prismatischer Hal-baryt, Mohs.—Schwerspath, Werner.—Baryte sulphatée, Hauy.
Specific Character.—Prismatic. Pyramid = ; ; . . Cleavage . . Fig. 45. Less distinct, . . (Fig. 33, 29, 27, 28.) Hardness = 3.0, — 3.5. Sp. gr. = 4.1, — 4.6.
Description.—Colours white, grey, black, blue,
Mineralogy. green, yellow, red, and brown. Occurs regularly crystallized; also in granular, lamellar, fibrous, and prismatic distinct concretions; massive, disseminated, reniform, botryoidal, and globular. Lustre alternates from splendid to shimmering, and resinous or pearly, inclining to vitreous. Fracture uneven, splintery, and earthy. Alternates from transparent to opaque. Brittle, and very easily frangible.
The varieties with uneven and splintery fracture are named compact h. spar; those in fine granular concretion granular h. spar; the lamellar varieties are named straight or curved lamellar h. spar, according to the direction of the lamellar concretion; the fibrous varieties fibrous h. spar; the radiated varieties radiated h. spar; those in prismatic concretions prismatic h. spar; the varieties which, on rubbing, emit a hepatic smell, fœtid h. spar, or hepatite; and those which occur in the earthy or powdery state, earthy h. spar.
Geognostic and Geographic Situations.—It occurs in veins, either alone or associated with various metalliferous formations of silver, copper, lead, cobalt, antimony, manganese, zinc, arsenic, iron, &c. in rocks of the primitive, transition, and secondary classes. Numerous localities of this mineral occur in Scotland, England, and Ireland.
4. Prismatoidal Baryte, or Celestine.—Jameson.
Prismatoidischer Hal-baryt, Mohs.—Coelestin, Werner.—Strontiane sulphatée, Haüy.
Specific Character.—Prismatic. Pyramid = ; ; ; . Cleavage, . More distinct, . (Fig. 45.) Less distinct, . . (Fig. 33, 29, 27, 28.) Hardness = 3.0, —3.5. Sp. gr. = 3.6, —4.0.
Description.—Colours white, blue, and red. Occurs regularly crystallized; in granular, fibrous, and radiated distinct concretions; massive and stalactitic. Lustre alternates from splendid to shimmering, and is pearly. Ranges from transparent to translucent on the edges.
Geognostic and Geographic Situations.—Occurs in limestone, in red sandstone, and gypsum, where it is associated with sulphur, and in vesicular cavities in amygdaloid. It has been found in sandstone near Inverness; in the amygdaloid of the Calton Hill; in the neighbourhood of Bristol; and near Knaresborough, in Yorkshire.
Genus VI.—LEAD SPAR.
Blei-baryt, Mohs.
Rhomboidal, pyramidal, prismatic. Hardness = 2.5, —4.0. Sp. gr. = 6.0, —7.3. If the hardness is above 3.5, the sp. gr. = 6.5, and more.
1. Di-prismatic Lead-Spar, or White Lead-Spar.—Jameson.
Di-prismatischer Blei-baryt, Mohs.—Plomb carbonatée, Haüy.
Specific Character.—Prismatic. Pyramid = ; ; . . Cleavage, . () = . (Fig. 43.) Hardness = 3.0, —3.5. Sp. gr. = 6.3, —6.6.
Description.—Principal colour white, occurs also black, yellow, brown, and grey. Occurs regularly crystallized; massive and cellular. Lustre externally ranges from splendid to shining; internally from shining to glistening, and is adamantine, inclining more or less to resinous and imperfect metallic. Fracture uneven and conchoidal. Ranges from transparent to opaque. Streak greyish-white.
Geognostic and Geographic Situations.—Occurs in veins in granite, gneiss, mica slate, and clay slate; also in limestone, greywacke, and in various secondary formations. Well known localities are Leadhills and Wanlockhead.
2. Rhomboidal Lead-Spar, or Green and Brown Lead-Spar.—Jameson.
Rhomboedrischer Blei-Baryt, Mohs.—Plomb Phosphaté, Haüy.
Specific Character.—Rhomboidal. Rhomboid = . Combination, di-rhomboidal. ; . Cleavage, ; . Hardness = 3.5, —4.0. Sp. gr. = 6.9, —7.3.
Description.—Colours green, brown, and sometimes yellow and white. Occurs regularly crystallized; also in granular, radiated, and curved lamellar concretions. Lustre externally shining, internally glistening, and resinous. Fracture uneven or splintery. Ranges from translucent to translucent on the edges. Streak white.
Geognostic and Geographic Situations.—Occurs in veins, and most abundantly in their upper part, in various rocks of the primitive, transition, and secondary classes, where it is associated with galena, white lead-spar, &c. Leadhills and Wanlockhead are well known localities.
3. Hemi-Prismatic Lead-Spar, or Red Lead-Spar.
Hemi-prismatischer Blei-Baryt, Mohs.—Roth Bleierz, Werner.—Plomb Chromaté, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Combination, hemi-prismatic. Cleavage, (nearly), , . (Fig. 30, 29, 28.) Hardness = 2.5. Sp. gr. = 6.0, —6.1.
Description.—Colour hyacinth red. Occurs regularly crystallized; also massive, and in flakes. Internally shining or splendid, and lustre adamantine. Fracture uneven, sometimes imperfect conchoidal. More or less translucent. Streak between lemon-yellow and orange-yellow. Nearly sectile, and easily frangible.
Geognostic and Geographic Situations.—Occurs in a granular quartz rock, associated with brown iron-stone, iron-pyrites, green lead-spar, native gold, galena, and quartz, in Siberia; also in sandstone in the Brazils.
Green Chromate of Lead.
The green and liver-brown coloured mineral, in small reniform and stalactitic forms, which accompanies the red lead-spar of Siberia, and also that of Brazil, according to Berzelius, contains the following constituent parts: Oxide of lead, 60.87 oxide of copper, 10.80; chromic acid, 28.33 = 100.
4. Pyramidal Lead-Spar, or Yellow Lead-Spar.
Pyramidaler Blei-Baryt, Mohs.—Gelb Bleierz, Werner.—Plomb molybdaté, Haüy.
Mineralogy. Specific Character.—Pyramidal. Pyramid = ; . Cleavage, . P. Hardness = 3.0. Sp. gr. = 6.5, —6.9.
Description.—Colour yellow. Occurs crystallized; also massive, in crusts, and cellular. Externally generally splendid and shining; internally shining or glistening, and lustre resinous-adamantine. Fracture uneven and conchoidal. Translucent, or translucent on the edges.
Geognostic and Geographic Situations.—Occurs in compact limestone, at Bleiberg in Carinthia; also in France and Saxony.
5. Prismatic Lead-Spar, or Sulphate of Lead.
Prismatischer Blei-Baryt, Mohs.—Vitriol Bleierz, Werner.—Plomb sulphaté, Haüy.
Specific Character.—Prismatic. Pyramid = ; ; . . Cleavage, . More distinct, . (Fig. 45.) Hardness = 3.0. Sp. gr. = 6.2, —6.3.
Description.—Colour white, seldom green or wine yellow, or blue (owing to blue malachite). Occurs regularly crystallized; in granular distinct concretions; also massive and disseminated. Lustre adamantine, and ranging from splendid to shining. Fracture conchoidal. Transparent or translucent.
Geognostic and Geographic Situations.—Occurs in galena veins, at Leadhills and Wanlockhead; and also in the Pary's Mine in Anglesea.
1. Corneous Lead Ore, or Muriat of Lead.—This rare mineral, which has been hitherto found only in Derbyshire, has not been described in a satisfactory manner.
Appendix of undetermined Lead-Spars.
2. Arseniate of Lead.—This is a rare mineral, hitherto not well described. Is found in Cornwall, and in several mines in France and Spain.
3. Plomb Gomme.—This rare mineral is of a reddish or yellowish brown colour, and the colours are disposed in stripes. Occurs small reniform, and in fibrous concretions. It is shining and translucent. It is a compound of oxide of lead, alumina, and water, according to Berzelius. It has been hitherto found only in the lead mines of Huelgoet in France.
N. B.—It bears a striking resemblance to hyalite.
Order III.—KERATE.
No metallic lustre. Streak white or grey. No single distinct cleavage. Hardness = 1.0, —2.0. Sp. gr. = 5.5.
Genus I.—CORNEOUS SILVER.
Hardness = 1.0, —2.0. Sp. gr. = 5.5, 5.6.
1. Hexahedral Corneous Silver.—Jameson.
Hexedrisches Perl Kerat, Mohs.—Hornerz, Werner.—Argent Muriaté, Haüy.
Specific Character.—Tessular. Cleavage not visible. Malleable. Sectile.
Description.—Colour pearl-grey, which passes into white, blue, and green; on exposure to light becomes brown. Occurs crystallized; in prismatic and
granular concretions; massive and in flakes. Lustre Mineralogy. ranges from shining to glistening, and is resinous. Fracture conchoidal. Translucent, or feebly translucent on the edges. Becomes shining in the streak.
Geognostic and Geographic Situations.—Occurs in silver-mines in Siberia, America, and has also been found in Cornwall.
Genus II.—CORNEOUS MERCURY.
Hardness = 1.0, 2.0. Sp. gr. unknown.
1. Pyramidal Corneous Mercury.—Jameson.
Pyramidales Perl Kerate, Mohs.—Quecksilber Hornerz, Werner.—Mercure, Muriaté, Haüy.
Specific Character.—Pyramidal. Pyramid unknown. Cleavage, , imperfect. Sectile.
Description.—Colour grey. Occurs generally in very minute crystals in vesicular cavities. Lustre shining and adamantine. Faintly translucent.
Order IV.—MALACHITE.
No metallic lustre. Colour blue, green, brown. No single distinct faces of cleavage. Hardness = 2.0, —5.0. Sp. gr. = 2.0, —4.6. If brown, in colour or in streak, the hardness = 3.0, and less; and the specific gravity above 2.5. If white in the streak, the specific gravity = 2.2, and less; and the hardness under 3.0.
Genus I.—COPPER GREEN.
Staphylin Malachit, Mohs.
Uncleavable. Hardness = 2.0, —3.0. Sp. gr. = 2.0, —2.2.
1. Uncleavable Copper Green.—Jameson.
Unheilbarer Staphylin-Malachit, Mohs. Kupfergrün, Werner. Cuivre Carbonaté, Haüy.
Specific Character.—Reniform, botryoidal. No cleavage.
Description.—Colour green. Occurs massive, disseminated, in crusts, reniform, and botryoidal. Lustre shining, glistening, and resinous. Fracture small, conchoidal. Ranges from translucent to translucent on the edges. Colour does not change in the streak.
Geognostic and Geographic Situations.—Occurs in copper-mines in Cornwall.
Genus II.—LIRICONITE.*
Lirikon-Malachit, Mohs.
Tessular, prismatic. Hardness = 2.5. Sp. gr. = 2.8, —3.0.
1. Prismatic Liriconite, or Lenticular Arseniate of Copper.—Jameson.
Prismatischer Lirikon-Malachit, Mohs.—Linsenerz, Werner.—Cuivre arseniaté, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, . . (Fig. 35, 30.) Streak pale verdigris-green, ... Sky-blue. Hardness = 2.5. Sp. gr. = 2.8, —3.0.
* From λιριον, pale, and χινα, dust (the streak).
Mineralogy. Description.—Colour blue, inclining more or less to verdigris-green. Occurs regularly crystallized. Lustre shining, glistening, and pearly, passing to vitreous. Fracture uneven. Translucent. Brittle, and uncommonly easily frangible.
Geognostic and Geographic Situations.—Occurs in the copper-mines of Cornwall.
2. Hexahedral Liriconite, or Cubical Arseniate of Iron.—Jameson.
Hexaedrischer Liricon-Malachit, Mohs.—Wurferlerz, Werner.—Fer Arseniaté, Hauy.
Specific Character.—Tessular. Combination, semi-tessular, with inclined planes. Cleavage, hexahedral. Streak pale olive-green, ...brown. Hardness = 2.5. Sp. gr. = 2.9, — 3.0.
Description.—Colour green. Occurs regularly crystallized, and massive. Lustre glistening and vitreous-resinous. Translucent, or translucent on the edges.
Geognostical and Geographical Situations.—Occurs in the copper-mines of Cornwall.
Genus III.—OLIVENITE.
Oliwen-Malachit, Mohs.
Prismatic. Colour or streak neither blue nor bright green. Hardness = 3.0, 4.0. Sp. gr. = 3.6, — 4.6.
1. Prismatic Olivinite, or Prismatic Arseniate of Copper.—Jameson.
Prismatischer Olivien-Malachit, Mohs.—Olivenerz, Werner.—Cuivre Arseniaté, Hauy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, . (Fig. 30.) Streak olive-green, ...brown. Hardness = 3.0. Sp. gr. = 4.2, — 4.6.
Description.—Principal colour olive-green, also yellow, brown, and white. Occurs regularly crystallized; in concretions which are scopiform fibrous, angulo-granular, and curved lamellar; massive and in drusy crusts. Lustre ranges from splendid to glimmering, and is resinous, inclining to pearly, or pearly. Ranges from transparent to opaque.
Geognostic and Geographic Situations.—Occurs in the copper-mines of Cornwall.
2. Diprismatic Olivinite.—Jameson.
Diprismatischer Olivien-Malachit, Mohs.
Specific Character.—Prismatic. Pyramid unknown. Cleavage unknown. Streak olive-green. Hardness = 4.0. Sp. gr. = 3.6, — 3.8.
Description.—Colours grass, olive, leek, and pistachio green. Occurs regularly crystallized. Lustre vitreous and pearly. Fracture conchoidal. Ranges from semi-transparent to translucent.
Geognostic and Geographic Situations.—Occurs in drusy cavities in micaceous clay-slate, with quartz and tile-ore; sometimes also with copper pyrites, at Libethen, in Hungary.
Genus IV.—BLUE MALACHITE, or BLUE COPPER.
Lazur Malachit, Mohs.
Prismatic. Blue. Hardness = 3.5, — 4. Sp. gr. = 3.5, — 3.7.
VOL. V. PART II.
1. Prismatic Blue Malachite.
Prismatischer Lazur Malachit, Mohs.—Kupferlazur, Werner.—Cuivre Carbonaté Bleu, Hauy.
Specific Character.—Prismatic. Pyramid unknown. Combination, hemi-prismatic. Cleavage prismatic. Streak blue.
Description.—Colours blue. Occurs regularly crystallized; in concretions which are scopiform and stellular, radiated, and also curved lamellar; massive, globular, botryoidal, reniform, stalactitic, and cellular. Lustre ranges from shining to glimmering, and is vitreous-resinous. Fracture conchoidal. Ranges from transparent to translucent on the edges.
A variety, in dull and fine dusty particles, is named earthy blue malachite, while the other varieties are denominated radiated blue malachite.
Geognostic and Geographic Situations.—Occurs in mineral veins and in beds in gneiss, mica slate, grey-wacke, limestone, and red sandstone. It occurs at the Lead Hills, and in various English copper and lead mines.
* Velvet Blue Copper.
Kupfersammlerz, Werner.
Description.—Occurs in bright blue, short capillary crystals. Lustre glistening and silky.
Geognostic and Geographic Situations.—It is a rare mineral; its only known locality is the Bannat, where it is associated with green malachite and brown iron-ore.
Genus V.—EMERALD MALACHITE.
Smaragd-Malachite, Mohs.
Hardness = 5.0. Sp. gr. = 3.2, — 3.4.
1. Rhomboidal Emerald Malachite.—Jameson.
Rhomboedrischer Smaragd-Malachit, Mohs.—Kupfersmaragd, Werner.—Cuivre Dioptase, Hauy.
Specific Character.—Rhomboidal. Rhomboid = . Cleavage rhomboidal. Streak green.
Description.—Colour emerald-green. Occurs regularly crystallized. Internally shining and pearly. Fracture conchoidal. Translucent, passing into semitransparent.
Geognostic and Geographic Situations.—Is a very rare mineral, and has hitherto been found only in the land of the Kirgies in Tartary.
Genus VI.—GREEN MALACHITE.
Habronem-Malachit, Mohs.
Prismatic. Colour or streak bright-green. Hardness = 3.5, — 5. Sp. gr. = 3.5, — 4.3.
1. Prismatic Green Malachite, or Phosphat of Copper.—Jameson.
Prismatischer Habronem-Malachit, Mohs.—Phospher Kupfererz, Werner.—Cuivre Phosphaté, Hauy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, (nearly.) (Fig. 30.) Streak emerald-green. Hardness = 5.0. Sp. gr. = 4.0, — 4.3.
Description.—Colours emerald-green, externally with a blackish tarnish, or spotted black. Occurs regularly crystallized; in scopiform fibrous concretions; massive, reniform, botryoidal. Lustre ranges
Mineralogy. from shining to glimmering and is resino-pearly. Fracture uneven. Opaque.
Geognostic and Geographic Situations.—Occurs at Virneberg, near Rheinbreitenbach, where it is disposed in veins in greywacke.
2. Diprismatic Green Malachite, or Common Malachite.—Jameson.
Diprismatischer Habronem-Malachit, Mohs.—Malachit, Werner.—Cuvre Carbonaté Vert, Häuy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, (nearly). (Fig. 33, 30.) Streak grass or apple green. Hardness = 3.5, ... 4.0. Sp. gr. = 3.5, ... 3.7.
Description.—Colour green. Occurs regularly crystallized; in distinct concretions, which are scopiform, fibrous, angulo-granular, and wedge-shaped; also massive, disseminated, tuberculate, stalactitic, reniform, botryoidal, fruticose, and cellular. Lustre ranges from shining to glimmering, and is silky. Fracture uneven, conchoidal, and even. Ranges from translucent to opaque.
Geognostic and Geographic Situations.—Occurs in veins that traverse primitive, transition, and secondary rocks; also in beds, and disseminated through rocks of different kinds. The copper-mine of Sand-lodge, in Shetland, formerly afforded fine specimens of the fibrous varieties; and fine masses are sometimes found in the copper-mines of Cornwall.
* ATACAMITE.
Streak leek...grass green, 2.5. Sp. gr. = 4.4.
1. Prismatic Atacamite, or Murat of Copper.—Jameson.
Cuvre Murat, Häuy.
Specific Character.—Prismatic. Cleavage very perfectly prismatic.
Description.—Colour green. Occurs regularly crystallized; in radiated and granular concretions; massive, disseminated, and in scaly particles. Lustre shining, glistening, and pearly. Translucent on the edges.
Geognostic and Geographic Situations.—Occurs in veins along with ores of copper in Chili, in the form of grains and scales in alluvial sand in the Desert of Atacama in Peru. Is also found in fissures of some Vesuvian lavas.
Order V.—MICA.
Cleavage montomous and very distinct. Hardness = 1.0, ... 4.5. Sp. gr. = 1.8, ... 5.6.
If metallic lustre, the sp. gr. is under 2.2. If no metallic lustre, the sp. gr. is above 2.2. If the streak is yellow, the sp. gr. is under 3.2.
If the hardness is above 2.5, it is rhomboidal. If the sp. gr. is under 2.5, it is metallic. If above 4.4, the streak is white or grey.
Genus I.—COPPER MICA.
Streak green. Hardness = 2.0. Sp. gr. = 2.5, ... 2.6.
1. Rhomboidal Copper Mica, or Micaceous Arseniate of Copper.—Jameson.
Rhombodrischer Euchlor-glimmer, Mohs.—Kupferglimmer, Werner.—Cuvre Arseniaté, Häuy.
Specific Character.—Rhomboidal. Rhomboid unknown. Cleavage . Streak emerald, ... apple-green.
Description.—Colour green. Occurs regularly crystallized; in granular concretions; massive, and disseminated. Internally splendid and pearly. Fracture uneven. Translucent and transparent. Sectile.
Geognostic and Geographic Situations.—Occurs in the copper-mines of Cornwall.
Genus II.—URAN-MICA, or URANITE.
Streak green, ... yellow. Hardness = 2.0, ... 2.5. Sp. gr. = 3.0, ... 3.2.
1. Pyramidal Uran Mica.—Jameson.
Pyramidal Euchlor-glimmer, Mohs.—Uran-glimmer, Werner.—Uran Oxyde, Häuy.
Specific Character.—Pyramidal. Pyramid = ; . Cleavage, .
Description.—Colours green and yellow. Occurs regularly crystallized; seldom massive, in scales, and in angulo-granular concretions. Lustre ranges from splendid to glistening, and is pearly. Transparent and translucent. Sectile. Not flexible. Easily frangible.
Geognostic and Geographic Situations.—Occurs in the copper and tin-mines of Cornwall.
* Uran Ochre.—This is the yellow or reddish coloured, soft, earthy looking, opaque mineral, occasionally associated with uran-mica, and also with uran-ore.
Genus III.—COBALT MICA, or RED COBALT.
Kobalt Glimmer, Mohs.
Prismatic. Hardness = 2.5. Sp. gr. = 4.0, ... 4.3.
1. Prismatic Cobalt Mica, or Red Cobalt.—Jameson.
Prismatischer Kobalt Glimmer, Mohs.—Rother Erd Kobalt, Werner.—Cobalt Arseniaté, Häuy.
Specific Character.—Prismatic. Pyramid unknown.
Combination hemi-prismatic, . Cleavage, .
(Fig. 29.) Streak red, ... green.
Description.—Colours red, rarely grey, green, and brown. Occurs regularly crystallized; in stellular and scopiform fibrous concretions; massive, disseminated, in crusts, reniform, and botryoidal. Lustre ranges from shining to dull, and is pearly and resinous. Fracture earthy and conchoidal. Sectile. Ranges from translucent to opaque.
Geognostic and Geographic Situations.—Occurs in veins in primitive and secondary rocks, and is met with in the coal-field around Edinburgh, and in the old lead-mines of Tyndrum in Perthshire.
* Cobalt Ochre.—There are three kinds of this mineral, which we shall now describe.
1. Black Cobalt Ochre.—Schwarz Erd Kobalt, Werner.
Colours black and occasionally brown. Occurs botryoidal, reniform, and in crusts. Lustre glimmering or dull. Fracture earthy and conchoidal. Opaque. Streak shining and resinous. Very soft, and sometimes friable.
Mineralogy. It is a compound of black oxide of cobalt, with arsenic and oxide of iron.
It occurs at Alderly Edge, Cheshire, in red sandstone.
2. Brown and Yellow Cobalt Ochre.—These differ from the preceding principally in colour, the tints being yellow and brown.
Genus IV.—ANTIMONY MICA, or WHITE ANTIMONY.
Antimon-glimmer, Mohs.
Hardness = 1.5, — 2.0. Sp. gr. = 5.0, — 5.6.
1. Prismatic White Antimony.—Jameson.
Prismatisches Antimon-glimmer, Mohs.—Weiss-spiess-glaserz, Werner.—Antimoine Oxyde, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage prismatoidal. Streak, white or grey.
Description.—Colours white and grey. Occurs regularly crystallized; in concretions which are scopiform and stellular radiated, and also granular. Lustre shining and pearly-adamantine. Translucent.
Geognostic and Geographic Situations.—It occurs in veins in primitive rocks, along with galena and grey and red antimony, in Bohemia, France, and Hungary.
* Antimony Ochre.—Spiesglanzocker, Werner.
Colours yellow, brown, and green. Occurs massive, disseminated, and in crusts. Dull. Earthy. Opaque. Very soft.
It always occurs in veins along with grey, and occasionally with red antimony, as in Cornwall.
Genus V.—BLUE IRON, or IRON MICA.
Eisen Glimmer, Mohs.
Prismatic. Streak white, grey, ... blue. Hardness = 2.0. Sp. gr. = 2.6, — 2.7.
1. Prismatic Blue Iron, or Phosphat of Iron.—Jameson.
Prismatisches Eisen Glimmer, Mohs.—Vivianit, Werner.—Fer Phosphate, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Combination hemiprismatic, . Cleavage, .
(Fig. 29.)
Description.—Colours blue and green. Occurs regularly crystallized; in scopiform and promiscuous fibrous concretions; massive, disseminated, and thinly coating. Lustre ranges from splendid to dull, and is pearly, inclining to adamantine. Ranges from transparent to opaque.
It sometimes occurs in a friable, or loosely cohering state, and is then composed of dull dusty particles, forming earthy blue iron.
Geognostic and Geographic Situations.—The crystallized varieties are found in Cornwall, those in fibrous concretions in Greenland, and the earthy and friable in our peat mosses.
Genus VI.—GRAPHITE.
Graphite Glimmer, Mohs.
Rhomboidal. Hardness = 1.0, — 2.0. Sp. gr. = 1.8, — 2.1.
1. Rhomboidal Graphite.—Jameson.
Rhomboedrischer Graphit-glimmer, Mohs.—Graphit, Werner.—Graphite, Haüy.
Specific Character.—Rhomboidal. Rhomboid unknown. Combination dirhomboidal. Cleavage, . Metallic aspect. Streak black.
Description.—Colour dark steel-grey, inclining to iron-black. Occurs regularly crystallized; in granular concretions; massive and disseminated. Lustre ranges from splendid to glimmering, and is metallic. Fracture scaly foliated, uneven, conchoidal, and slaty. Opaque. Sectile.
Geognostic and Geographic Situations.—It occurs in beds and imbedded masses, in primitive, transition, and secondary rocks. In Scotland it occurs in gneiss, in Glen Strath Farrar, in Inverness-shire; in the coal-formation in Ayrshire; and in England, in transition rocks near Borrodale in Cumberland.
Genus VII.—TALC-MICA.
Talc-Glimmer, Mohs.
Rhomboidal. Prismatic. Streak white, grey, ... green. Hardness = 1.0, — 2.5. Sp. gr. = 2.7, — 3.0.
1. Prismatic Talc-Mica, or Talc.—Jameson.
Prismatischer Talc-glimmer, Mohs.
Specific Character.—Prismatic. Pyramid unknown. (nearly.) Cleavage, . (Fig. 27.) Flexible. Hardness = 1.0, — 1.5. Sp. gr. = 2.7, — 2.8.
Description.—Colours green, sometimes passing into greenish black, also greenish white, grey, and rarely blue. Occurs regularly crystallized; in granular, fibrous, and prismatic concretions; massive, disseminated, and in amygdaloidal pieces. Lustre ranges from splendid to dull, and is pearly or resinous. Fracture slaty, scaly foliated, earthy, and uneven. Ranges from translucent to opaque.
The dark green varieties, which are generally opaque, are named chlorite; of those the regularly crystallized are named foliated chlorite; the slaty, chlorite slate; the massive, scaly foliated, common chlorite; the massive in scaly foliated feebly cohering particles, earthy chlorite; and the dull earthy varieties met with in vesicular cavities in amygdaloid, compact chlorite or green earth. The white and paler green varieties are named talc; of these the most translucent, and possessing the highest degree of lustre, are denominated common talc; while the grey and green varieties, with slaty fracture and inferior lustre, and inferior translucency, are named talc-slate or indurated talc.
Geognostic and Geographic Situations.—Occurs principally in primitive mountains, sometimes forming whole beds, as is the case with the varieties named chlorite slate, and talc-slate; other kinds, as common and earthy chlorite, occur disseminated, in veins, or dispersed through other minerals, as rock crystal, felspar, &c. while the compact chlorite, or green earth, appears principally in secondary amygdaloid. The most beautiful variety of the species, the common talc, occurs only in primitive rocks of limestone, mica-slate, &c. Examples of all the varieties are met with in the mountainous districts of Scotland and England.
1. Native Magnesia, or Hydrate of Magnesia.—
Mineralogy. Colours snow white, greenish white, and also grey. Occurs in prismatic concretions that point to the regular six-sided prism, also in granular concretions, and massive. Cleavage probably rhomboidal. Lustre shining and pearly. Semitransparent in the mass, and transparent in single folia. Streak white, and affords on paper a polished pearly trace. Hardness 1.5. Slightly elastic. Sp. gr. 2.13, Bruce. 2.336, Brewster. It is a pure hydrate of magnesia, the proportion of the constituent parts being magnesia 70. Water 30. Occurs in veins in serpentine, in the Shetland Islands and Portsoy.
2. Ophite, or Precious Serpentine.—Colours pure leek green, seldom grass and oil green. Occurs massive and disseminated. Glistening and resinous lustre. Fracture flat conchoidal, inclining to splintery. Translucent, or translucent on the edges. Hardness 3.5. Sp. gr. =2.5, —3.0.
3. Pikrolite.—Colour leek green. Massive, and in scopiform fibrous concretions. Lustre glimmering, or dull and silky. Fracture splintery or even. Translucent on the edges. Scratches calc-spar, and is scratched by felspar.
It occurs in small veins in beds of magnetic iron ore, subordinate to gneiss, and also in serpentine, in Sweden.
4. Nephrite.—Colours green, grey, and white. Massive, and in rolled pieces. Dull or glimmering. Fracture splintery. Strongly translucent. Difficultly frangible. Hardness =7.0. Sp. gr. =2.9, —3.1.
It occurs imbedded in various primitive rocks in Persia, Egypt, and Germany.
5. Steatite or Soapstone.—Colours white, red, and yellow, with frequent dendritic markings of black. Occurs massive, in crusts, and in false crystals. Fracture splintery and uneven. Dull or glimmering. Translucent on the edges. Sectile. Soft. Feels very greasy. It occurs principally in serpentine, as in that of the Shetland Islands and Cornwall.
N.B. The Pimelite of authors appears to be steatite coloured with nickel or chrome.
6. Figure-stone or Algalmatolite.—Colours grey, green, white, red, and brown. Massive. Dull or glimmering. Fracture conchoidal, or splintery, and slaty combined. Translucent. Resinous in streak. Feels rather greasy. The finest varieties are brought to Europe from China.
7. Magnesite.—Colours white, grey, and cream-yellow. Occurs massive, tuberculate, reniform, vesicular. Dull. Fracture conchoidal. Opaque. Hardness =3.3. Sp. gr. =2.881. Occurs in serpentine in Moravia, and in the Shetland Islands.
8. Meerschaum.—Colour white. Massive. Dull. Fracture earthy and conchoidal. Opaque or translucent on the edges. Very soft. Sectile. Adheres strongly to the tongue. Sp. gr. =0.988, —1.279. Occurs in serpentine in Cornwall, Shetland Islands, &c.
9. Lithomarge.—Colours white, grey, blue, green, red, and yellow, and these are sometimes disposed in a veined, spotted, clouded or striped manner. Occurs massive, disseminated, globular, and amygdaloid. Dull. Fracture earthy and flat conchoidal. Opaque. Shining in the streak. Soft. Sectile. Adheres strongly to the tongue. Feels fine and greasy. Sp. gr. =2.4.
It occurs in trap, porphyry, and serpentine rocks, in Mineralogy. Scotland and other countries.
10. Mountain Soap.—Colour blackish-brown. Massive. Dull. Fracture earthy. Opaque. Shining in the streak. Writes. Soft. Sectile. Adheres strongly to the tongue. Feels greasy. Occurs in secondary trap rock, in the Island of Skye.
11. Bole.—Colours brown, yellow, red, and black. Sometimes spotted and dendritic. Massive, and disseminated. Lustre glimmering. Fracture conchoidal. Feebly translucent. Soft. Feels greasy. Shining streak. Adheres to the tongue. Sp. gr. =1.922. Occurs imbedded in secondary trap-rocks in Scotland.
2. Rhomboidal Talc-Mica, or Common Mica.—
Jameson.
Rhombodrischer Talk-glimmer, Mohs.
Specific Character.—Rhomboidal. Rhomboid unknown. Combination dirhomboidal. Cleavage, R = ∞. Elastic. Hardness =2.0, —2.5. Sp. gr. =2.8, —3.0.
Description.—Colours grey, white, brown, black, red, and blue. Occurs regularly crystallized; in granular and prismatic concretions; massive and disseminated. Lustre ranges from splendid to shining; generally pearly, and sometimes semi-metallic. Fracture coarse, splintery, and scaly foliated. Ranges from transparent to feebly translucent. Sectile. Streak grey and dull.
The red and blue varieties, and which exhibit the splintery and scaly-foliated fractures, are described under the name Lepidolite.
Geognostic and Geographic Situations.—It occurs in all the primitive formations, and in most of those belonging to the transition and secondary classes; and therefore is an abundant mineral in this island. The lepidolite variety is rare; Dalmally may be mentioned as a British locality.
* Pinite.—Colours green, more or less deeply iron-shot. Occurs crystallized in six-sided prisms, in lamellar and granular concretions, and massive. Lustre glistening, glimmering, and resinous. Fracture uneven. Opaque. Soft. Sectile, not flexible. Feels rather greasy. Sp. gr. =2.914. Occurs imbedded in porphyry in Ben Gloe, and other mountains in Scotland.
Genus VIII.—PEARL-MICA.
Perl-glimmer, Mohs.
Rhomboidal. Hardness, =3.5, —4.5. Sp. gr. =3.0, —3.1.
1. Rhomboidal Pearl-Mica.—Jameson.
Rhombodrischer Perl-glimmer, Mohs.
Specific Character.—Rhomboidal. Rhomboid unknown. Combination dirhomboidal. Cleavage, R = ∞. Streak, white or grey.
Order VI.—SPAR.
No metallic lustre. Streak white or grey, ... and brown. Hardness, =3.5, —7.0. Sp. gr. =2.0, —3.7. If rhomboidal, the sp. gr. =2.2, and less, or the hardness =6.0. If hardness =4.0, the clea-
Mineralogy. vage is montomous. If hardness above 6.0, the sp. gr. is under 2.5, or above 2.8; and the lustre is pearly. If sp. gr. above 3.3, the combination is hemi or tetarto-prismatic, or the hardness = 6.0; and no adamantine lustre. If sp. gr. = 2.4, and less, there are traces of form and cleavage.
Prismatic. Cleavage montomous. Hardness = 3.6, —6.0. Sp. gr. = 3.6, —3.4. If hardness = 6.0, the lustre is metallic-pearly.
Diatomer Schiller-spath, Mohs.—Schiller-stein, Werner.—Diallage Metalloide, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage prismatoidal. Metallic pearly lustre. Hardness = 3.5, —4.0. Sp. gr. = 2.6, —2.8.
Description.—Colours green, grey, and brown. Occurs in granular concretions; disseminated, and seldom massive. Lustre shining or splendid, and metallic-pearly. Translucent on the edges, or opaque. Dull streak.
Geognostic and Geographic Situations.—Occurs imbedded in serpentine in the Shetland Islands, and in secondary trap-rocks in the middle district of Scotland.
Axentheilender Schiller-spath, Mohs.—Körniger Strahlstein, Werner.—Diallage Verte, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, . (Fig. 27.) Common pearly lustre. Hardness = 4.5, —5.5. Sp. gr. = 3.0, —3.2.
Description.—Colour green; massive and disseminated. Internally shining and glistening. Translucent on the edges, or translucent.
Geognostic and Geographic Situations.—Occurs in primitive rocks in Shetland Islands, and Mainland of Scotland.
Hemiprismatischer Schiller-Spath, Mohs.—Blättriger Anthophyllite, Werner.—Diallage Metalloide, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Combination hemiprismatic. Cleavage, . Less perfect, . (Fig. 29, 35, 28.) Lustre metallic-pearly. Hardness = 4.0, —5.0. Sp. gr. = 3.0, —3.3.
Description.—Colours brown and grey. Occurs in granular concretions. Lustre shining. Cleavage
sometimes appears fibrous. Translucent on the edges. Streak white.
Geognostic and Geographic Situations.—Occurs in serpentine in Shetland; in greenstone in the Island of Skye, and near Portsoy; and in other parts of Scotland.
Prismatoidischer Schiller-Spath, Mohs.—Paulit, Werner.—Hypersthene, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, . Less perfect, (nearly). . (Fig. 29, 30, 28.) Lustre metallic-pearly. Hardness = 6.0. Sp. gr. = 3.3, —3.4.
Description.—Colours greenish and greyish black; also copper-red and brown. Occurs in granular and lamellar concretions, and massive. Lustre shining. Opaque or feebly translucent.
Geognostic and Geographic Situations.—Occurs in greenstone in the Island of Skye; also in Banffshire and the Shetland Islands.
Prismatischer Schiller-Spath, Mohs.—Strahliger Anthophyllit, Werner.—Anthophyllite, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, . Rather less perfect, (nearly). . (Fig. 28, 30, 29.) Lustre almost metallic-pearly. Hardness = 5.0—5.5. Sp. gr. = 3.0, —3.3.
Description.—Colours yellowish grey and yellowish brown. Occurs crystallized in reed-like crystals; in scopiform and promiscuous radiated concretions; also massive. Translucent on the edges.
Geognostic and Geographic Situations.—Occurs in primitive rocks, near Drimnatrochit, in Inverness-shire.
Prismatic. Hardness = 5.0, —7.0. Sp. gr. = 3.5, —3.7.
Disthen Spath, Mohs.—Kyanite and Rhatizit, Werner.—Disthene, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Combination, tetarto-prismatic. Cleavage, two faces, the one more distinct than the other. Incidence = .
Description.—Colours blue and bluish green. Occurs regularly crystallized; in distinct concretions, which are granular and radiated, which latter are sometimes scopiform and stellular; also massive and
* From δια, through; and τιμω, I cut; easily cleavable in one direction.
† From αξω, the axis; and τιμω, I cut; cleavable perpendicular to the axis.
Mineralogy. disseminated. Lustre splendid and pearly. Translucent and transparent.
Geognostic and Geographic Situations.—It occurs in primitive rocks in the Shetland Islands; also in Banffshire and Aberdeenshire.
Genus III.—SPODUMENE.
Hardness = 6.5, —7.0. Sp. gr. = 3.0, —3.1.
1. Prismatic Spodumene.—Jameson.
Spodumen, Werner.—Triphane, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, (nearly). Some-what more distinct, . Not blue. (Fig. 30, 29.)
Description.—Colours greenish white and green. Occurs massive, and in large granular concretions. Lustre shining, glistening, and pearly. Fracture uneven. Translucent. Uncommonly easily frangible.
Geognostic and Geographic Situations.—Occurs in primitive rocks in Sweden and in Ireland.
Genus IV.—PREHNITE.
Axotomer Triphan-Spath, Mohs.—Prehnite, Werner and Haüy.
Hardness = 6, —7. Sp. gr. = 2.8, —3.0. Not blue.
1. Axotomous Prehnite.—Jameson.
Specific Character.—Prismatic. Pyramid unknown. Cleavage (nearly). More distinct . (Fig. 30, 27.)
Description.—Colours green, grey, and white. Occurs crystallized; in granular and in scopiform and stellular fibrous distinct concretions; massive and reniform. Lustre shining, glistening, and pearly. Fracture uneven. Ranges from transparent to translucent.
Geognostic and Geographic Situations.—The more highly crystallized varieties have hitherto been found principally in primitive rocks, while the fibrous or less perfectly crystallized varieties occur principally in secondary trap-rocks. The secondary trap-rocks of Scotland afford many localities of this mineral.
Karpholite.—The colour of this rare mineral is yellow. It occurs in fine prismatic concretions. Its hardness is unknown, but its sp. gr. = 2.935. It has hitherto been found only at Schlackenwalde in Bohemia.
Genus V.—DATOLITE.
Dystom-Spath, Mohs.
Prismatic. Internally, lustre resinous. Colour not blue. Hardness = 5.0, —5.5. Sp. gr. = 2.9, —3.0.
1. Prismatic Datolite.—Jameson.
Prismatischer Dystom-Spath, Mohs.—Chaux Boratée Siliceuse, Haüy.
Specific Character.—Prismatic. Pyramid = ; ; . Combination hemiprismatic. . Cleavage, imperfect. (Fig. 30.)
Description.—Most frequent colours white and Mineralogy grey, seldom red, green, and yellow. Occurs regularly crystallized; in granular, scopiform, and stellular, fibrous, and curved lamellar concretions; massive, reniform, and botryoidal. Lustre ranges from shining to dull, and is resinous or pearly. Fracture conchoidal, uneven, and earthy. Ranges from transparent to opaque.
The reniform and botryoidal varieties in fibrous concretions are named Botryolite; the earthy-looking and botryoidal Earthy Botryoidal Datolite; all the others Common Datolite.
Geognostic and Geographic Situations.—Occurs in beds of magnetic iron-ore, subordinate to gneiss, near Arendal in Norway, and rarely in other parts of Europe.
Genus VI.—ZEOLITE.
Kuphon-Spath, Mohs.
Tessular, rhomboidal, pyramidal, prismatic. Hardness = 3.5, —6.0. Sp. gr. = 2.0—2.5. If the most distinct cleavage be parallel to a rectangular prism, the sp. gr. = 2.4, and less.
1. Trapezoidal Zeolite, or Leucite.—Jameson.
Trapezoidal Kuphon-Spath, Mohs.—Leuzit, Werner.—Amphigène, Haüy.
Specific Character.—Tessular. Cleavage hexahedral, dodecahedral, imperfect. Hardness = 5.5, —6.0. Sp. gr. = 2.4, —2.5.
Description.—Colours white and grey. Occurs regularly crystallized; in granular concretions, and in roundish grains. Lustre shining or glistening, and vitreo-resinous. Fracture flat conchoidal. Ranges from transparent to opaque.
Geognostic and Geographic Situations.—Occurs in imbedded grains and crystals in older lavas, and associated with garnet, hornblende, quartz, glassy feldspar, in the ejected masses of Monte Somma, and the extinct volcanoes on the Rhine, afford examples of leucite in both situations.
2. Dodecahedral Zeolite, or Sodalite.—Jameson.
Dodecaedrischer Kuphon-Spath, Mohs.—Sodalite, Thomson.
Specific Character.—Tessular. Cleavage dodecahedral, and perfect. Hardness = 5.5, —6.0. Sp. gr. = 2.2, —2.4.
Description.—Colour green. Occurs in rhomboidal dodecahedrons, and massive. Lustre shining or glistening, and vitreo-resinous. Fracture conchoidal. Translucent.
Geognostic and Geographic Situations.—Occurs in mica-slate in West Greenland.
3. Hexahedral Zeolite, or Analcime.—Jameson.
Hexaedrischer Kuphon-Spath, Mohs.—Analcime, Haüy.—Kubizit, Werner.
Specific Character.—Tessular. Cleavage hexahedral, imperfect. Hardness = 5.5. Sp. gr. = 2.0, —2.2.
Description.—Colours white and red. Occurs regularly crystallized; in angulo-granular concretions, and massive. Lustre shining, glistening, and vitreous. Fracture uneven, or conchoidal. Ranges from transparent to translucent.
Mineralogy. Geognostic and Geographic Situations.—Occurs in secondary greenstone rocks in Fife-shire, Salis-bury Crag, near Edinburgh, and in the same rock in many other parts of Scotland.
4. Paratomous Zeolite, or Cross-stone.—Jameson.
Paratomer Kuphon-spath, Mohs.—Kreutzstein, Werner—Harmotome, Haüy.
Specific Character.—Prismatic. Pyramid unknown.
Cleavage . . . (Fig. 29, 28.) Hardness = 4.5. Sp. gr. = 2.3, —2.4.
Description.—Colours white and grey, sometimes also yellow and red. Most frequently in regular crystals, seldom massive. Lustre shining, glistening, and vitreo-pearly. Fracture conchoidal and uneven. Translucent.
Geognostic and Geographic Situations.—Occurs in galena veins in the mines of Strontian in Argyle-shire, and in secondary trap-rocks in Dumbarton-shire, and other parts of Scotland.
5. Rhomboidal Zeolite, or Chabasite.—Jameson.
Rhomboedrischer Kuphon-Spath, Mohs.—Chabasie, Haüy—Schabasit, Werner.
Specific Character.—Rhomboidal. Rhomboid, = . Cleavage rhomboidal. Hardness = 4.0, —4.5. Sp. gr. = 2.0, —2.1.
Description.—Colour white. Occurs regularly crystallized, seldom massive. Externally splendid, internally glistening and vitreous. Fracture conchoidal and uneven. Translucent.
Geognostic and Geographic Situations.—Occurs in various secondary trap-rocks, especially amygdaloid, and is not unfrequent in the trap-rocks of Scotland.
6. Diatomous Zeolite, or Laumonite.—Jameson.
Diatomer Kuphon-spath, Mohs.—Laumonite, Werner, Haüy.
Specific Character.—Prismatic. Pyramid = ; ; . . Combination hemi-prismatic, . Cleavage,
. More perfect, . (Fig. 28, 29.) Hardness unknown. Sp. gr. = 2.3, —2.4.
Description.—Colour white. Occurs regularly crystallized, and in granular distinct concretions. Lustre shining, glistening, and pearly. When fresh is transparent; but on exposure to the atmosphere it very soon becomes opaque, and so soft as to yield to the pressure of the finger. Uncommonly easily frangible.
Geognostic and Geographic Situations.—This mineral occurs in secondary trap-rocks in various parts of Scotland and Ireland.
7. Prismatic Zeolite, or Mesotype.—Jameson.
Prismatischer Kuphon-spath, Mohs.—Mesotype, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, . (Fig. 30.) Hardness = 5.0, —5.5. Sp. gr. = 2.0, —2.3.
Description.—Colours white, red, yellow, and yellowish-brown. Occurs regularly crystallized; in distinct concretions which are scopiform and stellular
fibrous, granular, and curved lamellar; reniform, cor. Mineralogy. alloidal, in plates and crusts. Lustre ranging from shining to dull, and is pearly. Fracture, in some varieties, coarse earthy. Ranges from nearly transparent to opaque.
The yellow and brown varieties, with striped colour delineations, and in which the fibrous and granular concretions are intersected by lamellar, are named Natrolite; those with earthy fracture and very soft, Pearly zeolite; while the other varieties are named Fibrous zeolite.
Geognostic and Geographic Situations.—Occurs principally in drusy cavities, or in veins in secondary trap-rocks in many places in Scotland. The natrolite is the rarest variety in Scotland.
8. Prismatoidal Zeolite, or Stilbite.—Jameson.
Prismatoidischer Kuphon-spath, Mohs.—Stilbit, Haüy—Strahl-zeolith, Werner.
Specific Character.—Prismatic. Pyramid = ; ; . . Cleavage, , very perfect. (Fig. 29.) Hardness = 3.5, —4.0. Sp. gr. = 2.0, —2.2.
Description.—Colour white, sometimes grey, yellow, and red. Occurs regularly crystallized; in granular, and in scopiform, and stellular prismatic concretions; also massive and globular. Externally splendid. Internally shining and pearly. Alternates from transparent to translucent.
Geognostic and Geographic Situations.—Occurs abundantly in secondary trap-rocks in many districts in Scotland.
9. Hemi-prismatic Zeolite.—Jameson.
Hemi-prismatischer Kuphon-spath, Mohs.—Blätter Zeolith, Werner. Stilbite, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Combination, hemiprismatic . Cleavage, , very perfect. (Fig. 29.) Hardness = 3.5, —4.0. Sp. gr. = 2.0, —2.2.
Description.—Colours white, grey, red, and brown. Occurs regularly crystallized; in granular and lamellar distinct concretions. Fracture conchoidal. Externally, lustre splendid, shining, and vitreous; internally, shining and pearly. Ranges from transparent to translucent on the edges.
Geognostic and Geographic Situations.—Occurs in drusy cavities in secondary trap-rocks in the Hebrides and Mainland of Scotland.
10. Pyramidal Zeolite, or Apophyllite.—Jameson.
Pyramidal Kuphon-spath, Mohs.—Albin, Werner. Mesotype époincée, Haüy.
Specific Character.—Pyramidal. Pyramid unknown. Cleavage, , very perfect. [] imperfect. Hardness = 4.5, —5.0. Sp. gr. = 2.2, —2.5.
Description.—Colour white. Occurs regularly crystallized; in straight and curved lamellar distinct concretions; massive and disseminated. Surface of the cleavage strongly iridescent. Externally splendid, but only the terminal planes of the prism pear-
Mineralogy. ly; internally glistening and vitreous. Ranges from transparent to translucent.
Geognostic and Geographic Situations.—Occurs in secondary trap-rocks in the Hebrides and other parts of Scotland.
11. Axotomous Zeolite, or Ichthyophthalmite.
Axotomer Kuphon-spath, Mohs. Ichthyophthalm, Werner. Apophyllite, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, , very distinct. Less distinct . . (Fig. 27, 29, 28.) Hardness = 4.5, —5.0. Sp. gr. = 2.2, —2.5.
Geognostic and Geographic Situations.—Occurs in secondary trap-rocks in Scotland.
Genus VI.—PETALITE.
Petalin-spath, Mohs.
Prismatic. Hardness = 6.0, —6.5. Sp. gr. = 2.4, —2.5.
1. Prismatic Petalite.—Jameson.
Prismatischer Petalin-spath, Mohs.
Specific Character.—Prismatic. Pyramid unknown.
Cleavage, . .
Description.—Colours red and white. Occurs massive; internally glistening, shining, and nearly pearly. Translucent. Brittle, and rather easily frangible.
Geognostic and Geographic Situations.—It has hitherto been found only in the island of Uton in Sutherland, in large masses, containing spodumene, felspar, quartz, mica, tourmaline, and ores of iron, arsenic, and silver.
Genus VII.—FELSPAR.
Rhomboidal, pyramidal, prismatic. Cleavage not very perfect. Axotomous. Hardness = 5.0, —6.0. Sp. gr. = 2.5, —2.8. If Sp. gr. = 2.7, and more, the cleavage planes are perpendicular to each other.
1. Rhomboidal Felspar, or Nepheline.—Jameson.
Rhomboedrischer feldspath, Mohs. Nepheline, Haüy and Werner.
Specific Character.—Rhomboidal. . Combination, di-rhomboidal. ; . Cleavage, . . Hardness = 6.0. Sp. gr. = 2.5, —2.6.
Description.—Colours white and grey. Occurs regularly crystallized, and massive. Externally splendid, internally shining and vitreous. Fracture conchoidal. Translucent, passing into transparent.
Geognostic and Geographic Situations.—Occurs in drusy cavities in granular foliated limestone, with meionite, Vesuvian, pleonaste, rhomboidal garnet, mica, &c. in the ejected masses on Monte Somma, near Naples.
2. Prismatic Felspar, or Common Felspar.—Jameson.
Prismatischer Feldspath, Mohs.
Prismatic. Pyramid = ; ; . . Combination .
Cleavage, . . Both very perfect. Less
distinct, . Sometimes only one of the faces. (Fig. 44.) Hardness = 6.0. Sp. gr. = 2.5, —2.8.
Description.—Colours white, grey, green, blue, red, and brown; and sometimes with pearly opalescence, and beautiful changeability of colour. Occurs regularly crystallized; in distinct concretions, which are angulo-granular and lamellar; massive and disseminated. Lustre ranges from splendid to glistening, and even to dull, and is vitreous-pearly, or vitreous. Fracture conchoidal, splintery, slaty, and earthy. Ranges from transparent to opaque.
The transparent and translucent white-coloured varieties, with the silvery or pearly opalescence, are named adularia; the white and grey transparent varieties usually in small crystals, which are traversed by numerous rents, are named glassy felspar; the translucent varieties, with various shades of colour, such as white and red, and rarely blue and green, are the most abundant, and hence are named common felspar; the dark-grey varieties, with the beautiful changeability of colour, are named Labrador felspar, from the country where they were first found; the feebly translucent compact varieties, with splintery fracture, are named compact felspar; the slaty varieties, with feeble lustre and translucency, are named slaty felspar or clinkstone; the varieties, in a comparatively loose state of aggregation, and without lustre and transparency, according to their degrees of compactness, are named porcelain earth, earthy felspar, and claystone.
Geognostic and Geographic Situations.—Felspar is one of the most abundant minerals in nature, as it occurs in most of the principal rock formations. It abounds in the Alpine districts of Scotland, England, and Ireland, in granite, syenite, gneiss, porphyry, trap, and quartz rocks.
3. Pyramidal Felspar, or Scapolite.—Jameson.
Pyramidal Feldspath, Mohs.—Meionite, Scapolite, Schmelzstein, Werner.—Paranthine, Meionite, Wernerite, Dipyre, Haüy.
Specific Character.—Pyramidal. Pyramid = ; . Cleavage, . More perfect, . . Hardness = 5.0, —5.5. Sp. gr. = 2.5, —2.8.
Description.—Colours white, grey, green, red, and black. Occurs regularly crystallized; in distinct concretions, which are scopiform, fibrous, or radiated, and angulo-granular; massive and disseminated. Lustre ranges from splendid to glistening, and is pearly, resino-vitreous, and resino-pearly. Fracture conchoidal, uneven. Ranges from transparent to opaque.
The white and more transparent and highly crystallized varieties are named Meionite, while the others have received the names Scapolite, Paranthine, Wernerite, Dipyre, and Schmelzstein.
Geognostic and Geographic Situations.—The meionite varieties are found in drusy cavities in granular foliated limestone, along with nepheline, augite, mica, pleonaste, garnet, and calcareous spar, on
Mineralogy. Monte Somma, near Naples; the scapolite varieties occur in beds of magnetic ironstone and iron pyrites, in gneiss, along with quartz, felspar, mica, hornblende, epidote, garnet, augite, &c. at Arendal, in Norway; also in Sweden, Finland, Saxony, Pyrenees, &c.
* Elaolite.—Muschlicher Wernerite, Fettstein, Werner. Lythodes, Karsten. Purre grasse, Haüy.
Specific Character.—Prismatic. Cleavage, , . Less distinct, . Hardness, , . Sp. gr. , .
Description.—Colours muddy flesh-red and greenish-grey, inclining to blue. Occurs massive. Lustre glistening and resinous. Fracture flat conchoidal, inclining to splintery and uneven. Translucent.
Geognostic and Geographic Situations.—Occurs imbedded in syenite, along with titanite, zircon, and molybdena, at Laurwig, and Friedrichsværn, in Norway.
Genus VIII.—AUGITE.
Prismatic. Lustre not metallic-pearly. Hardness , . Sp. gr. , . If the hardness is above 6.0, the sp. gr. , and more. If the sp. gr. is under 3.0, the cleavage is very perfect, and in the direction of oblique-angular prisms.
1. Paratomous Augite.—Jameson.
Paratomer Augit, Mohs.—Augit, Werner.—Pyroxene, Haüy.
Specific Character.—Prismatic. Pyramid ; ; . . Combination hemi-prismatic. . Cleavage, , . . Sometimes . (Fig. 32, 29, 28, 38.) Hardness , . Sp. gr. , .
Description.—Colours green, black, and brown; also grey and white. Occurs regularly crystallized; in granular and fibrous concretions; massive and disseminated. Lustre ranges from splendid to shimmering, and is vitreo-resinous, resinous-pearly, and resinous. Fracture conchoidal and uneven. Ranges from transparent to translucent on the edges.
Those varieties in which the colours are white and pale green, generally crystallized, with a vitreous external, and pearly internal lustre, and translucent, are named Diopside, Musite, Alalite, and by some Baikalite; those, again, in which the colours are darker green and muddy grey, less frequently crystallized, but disposed in straight, lamellar, and granular concretions, with a shining, vitreous, or pearly lustre, and translucent on the edges, are named Sahlite, Pyrogome, Fassaite, Malacolite, and by some Baikalite; other varieties, in which the colours are black and dark green, with conchoidal and uneven fracture, resinous lustre, and opaque or faintly translucent on the edges, are named Conchoidal Augite and Common Augite; those varieties in which the colours are principally leek-green and greenish-black, generally in loosely aggregated angulo-granular concretions, with a shining vitreo-resinous lustre,
uneven fracture, and ranging from translucent to opaque, are named Coccolite and Granular Augite; and, lastly, the fibrous varieties have been described as Amianthus.
Geognostic and Geographic Situations.—The diopside varieties are found imbedded in serpentine, and associated with magnetic iron-ore in Piedmont; the sahlite in beds of primitive trap, limestone, and magnetic iron-ore, subordinate to gneiss and mica slate in Scotland, Ireland, and Scandinavia; the conchoidal augite and common augite occur principally in secondary trap rocks; and the coccolite and granular augite in the iron mines of Arendal, in Norway, in gneiss.
2. Hemi-prismatic Augite, or Hornblende.—Jameson.
Hemi-prismatischer Augit-spath, Mohs.—Hornblende, &c. Werner.—Amphibole, Haüy.
Specific Character.—Prismatic. Pyramid ; ; . . Combination, hemi-prismatic, . Cleavage,
. Less distinct, . . (Fig. 32, 29, 28.) Hardness , . Sp. gr. , .
Description.—Colours green, white, black, grey, blue, and brown. Occurs regularly crystallized; in fibrous, radiated, and granular distinct concretions. Lustre ranges from splendid to feebly shimmering, and lustre vitreo-pearly, pearly, or vitreous, and vitreo-resinous. Fracture conchoidal, uneven, and slaty. Alternates from transparent to opaque.
The varieties with dark green and black colours, in granular and fibrous concretions, and in which the lustre ranges from splendid to shining, and is pearly or pearly-vitreous, and the transparency from transparent to translucent on the edges, are named Hornblende and Carinthine; the varieties with light green, and also greenish-grey, and sometimes brown and yellow colours, rarely crystallized (and then generally in reed-like crystals), more frequently massive, and in radiated, fibrous, and granular concretions, with a pearly or vitreous, splendid, shining, or glistening lustre, and transparency varying from transparent to opaque, are named Actinolite and Calamite; the white and blue varieties, disposed in fibrous, radiated, and granular concretions, with a lustre which is shining, or glistening and pearly, or vitreous-pearly, and ranging from translucent to transparent on the edges, are named Tremolite; other varieties, in which the colours are white, green, yellow, blue, and brown, and disposed in flexible, shining, silky, fibrous concretions, are named Flexible Asbestos, or Amianthus; others, which are of a white colour, or grey colour, and disposed in minute promiscuous fibrous concretions, and so light as to swim in masses in water, are named Mountain Cork; those in which the colours are generally green, and disposed in straight, shining, pearly, rigid, fibrous concretions, are named Rigid, or Common Asbestos; and, lastly, those varieties in which the colour is wood-brown, and in general aspect much resembling fossil wood, are named Rock-wood, or Lignous Asbestos.
Mineralogy. Geognostic and Geographic Situations.—The hornblende varieties abound in primitive and transition rocks, and are also met with in those of the secondary class; those named actinolite and tremolite scarcely occur in secondary rocks, being confined principally to those of the primitive class; while the asbestine varieties are principally met with in the serpentine rocks of primitive and transition mountains. Numerous localities of this species occur in Scotland, England, and Ireland.
3. Prismatoidal Augite, or Epidote.—Jameson.
Prismatoidischer Augit-spath, Mohs.—Epidote, Häuy.
Specific Character.—Prismatic. Pyramid unknown. Combination hemi-prismatic. Cleavage, two faces, of which one is more distinct than the other. Incidence . Hardness , . Sp. gr. , .
Description.—Colours green and grey. Occurs regularly crystallized; in granular, fibrous, and prismatic concretions. Lustre ranges from splendid to glimmering, and is resino-pearly. Fracture conchoidal, uneven, splintery, and sometimes nearly earthy. Ranges from transparent to translucent on the edges. Brittle, and easily frangible.
The green varieties are named simply epidote, or pistacite; while the grey and less perfectly crystallized varieties are named zoisite.
Geognostic and Geographic Situations.—It occurs principally in primitive rocks, such as gneiss, mica-slate, syenite, &c. Inverness-shire, Ross-shire, the Shetland Islands, and other parts of Scotland, afford many varieties of it.
4. Prismatic Augite, or Tabular-Spar.—Jameson.
Prismatischer Augit-spath, Mohs.—Schaalstein, Werner.—Spath en Tables, Häuy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, (nearly). . . Sp. gr. , .
Description.—Colour white. Occurs in granular and lamellar concretions; also massive and disseminated. Lustre ranges from shining to glistening, and is pearly-vitreous. Fracture splintery. Translucent. Brittle.
Geognostic and Geographic Situations.—Occurs in primitive rocks in the Bannat, and in rocks of the same description in the island of Ceylon.
Genus IX.—AZURE-SPAR.
Colour blue. Hardness , . Sp. gr. , .
1. Prismatic Azure-Spar.—Jameson.
Lazulit, Werner.—Lazulite, Häuy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage . (Fig. 30.) Colour lively. Hardness , .
Description.—Colour blue. Occurs massive. Fracture uneven. Opaque. Very feebly translucent on the edges. Easily frangible.
Geognostic and Geographic Situations.—Occurs
imbedded in quartz, in the district of Vorau, in Mineralogy. Stiria.
2. Prismatoidal Azure-Spar.—Jameson.
Blauspath, Werner.—Feldspath, Häuy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage prismatoidal. Colour pale. Hardness , .
Description.—Colour blue. Occurs massive and disseminated. Lustre glistening. Fracture splintery. Feebly translucent. Yields a greyish-white streak.
Geognostic and Geographic Situations.—Occurs in primitive rocks in Stiria.
* 1. Azure-Stone, or Lapis Lazuli.
Lazurstein, Werner.
Tessular. Form dodecahedral. Cleavage unknown, imperfect. Azure blue. Hardness , . Sp. gr. , .
Colour blue. Occurs massive, with disseminated marble and iron pyrites. Lustre glistening and glimmering. Fracture uneven. Feebly translucent on the edges.
Geognostic and Geographic Situations.—Occurs in rocks of limestone in Persia and China.
2. Hauyne-Lateralite.—Häuy.
Prismatic. Cleavage . More distinct , Blue. Scratches glass. Sp. gr. , Gmelin. 3.333, Gismondi.
3. Calaitte or Mineral Turquois.
Form unknown. Massive. Blue...green. Streak white. Hardness . Sp. gr. ....
4. Amblygonite.—Breithaupt and Mohs.
Prismatic. . Cleavage, . Hardness . Sp. gr. .
5. Diaspore.—Häuy and Mohs.
Prismatic. Cleavage, nearly. More distinct . Scratches glass. Sp. gr. .
6. Gehlenite.—Mohs and Häuy.
Pyramidal, or prismatic. Cleavage unknown, or very imperfect. Hardness , . Sp. gr. , .
Order VII.—GEM.
No metallic lustre. Streak white or grey. Hardness , . Sp. gr. , . If hardness , and less, the sp. gr. , and less, and no traces of form or cleavage. If sp. gr. is less than 3.8, there is no pearly lustre.
Genus I.—ANDALUSITE.
Prismatic. Cleavage, not prismatoidal. Hardness . Sp. gr. , .
1. Prismatic Andalusite.—Jameson.
Prismatischer Andalusit, Mohs.—Andalusit, Werner.—Feldspath apyre, Häuy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, . . . (Fig. 30, 29, 28.)
Description.—Colours red and grey. Occurs re-
Mineralogy. gularly crystallized and massive. Lustre shining, glistening, and vitreous. Fracture uneven. Feebly translucent.
Geognostic and Geographic Situations.—Occurs in gneiss in Shetland Islands, and in Aberdeenshire.
* Fibrolite.—Bourne.
Prismatic. . Cleavage imperfect. Hardness more considerable than quartz, and sp. gr. = 3.214. Occurs in the Carnatic.
* Chiastolite. Hohlspath, Werner.—Macle, Hauy.
Prismatic. . nearly. Cleavage, . . . All of them imperfect. Hardness = 5, — 5.5. Sp. gr. = 2.9, — 3.0. Occurs in clay-slate near Keswick in Cumberland, and near Balahulish in Argylshire.
Genus II.—CORUNDUM.
Tessular, rhomboidal, prismatic. Hardness = 8.0, — 9.0. Sp. gr. = 3.5, — 4.3. If prismatic, the sp. gr. = 3.7, and more, and hardness = 8.5. If colour red, and sp. gr. = 3.7, and more, the hardness = 9.0.
1. Dodecahedral Corundum.—Jameson.
Dodecaedrischer Corund, Mohs.—Spinell and Zeilanit, Werner.—Spinelle, Hauy.
Specific Character.—Tessular. Cleavage, octahedral, but obtained with difficulty. Hardness = 8.0. Sp. gr. 3.5, — 3.8.
Description.—Colours red, and sometimes green, black, blue, yellow, brown, and white. Occurs regularly crystallized. Lustre splendid and vitreous. Fracture conchoidal. Ranges from transparent to translucent on the edges.
The dark green and black varieties, which are only translucent on the edges, are named ceylanite; and all the others spinell or spinell-ruby.
Geognostic and Geographic Situations.—The ceylanite varieties occur in the sand of rivers in Ceylon; the others also in Ceylon, Pegu, and other countries.
2. Octahedral Corundum or Automalite.—Jameson.
Octaedrischer Corund, Mohs.—Automalite, Werner.—Spinelle Zincifere, Hauy.
Specific Character.—Tessular. Cleavage, octahedral, and easily obtained. Hardness = 8. Sp. gr. = 4.1, — 4.3.
Description.—Colour green. Occurs regularly crystallized. External lustre pearly, inclining to semi-metallic, internally shining and resinous. Fracture conchoidal. Opaque or faintly translucent on the edges.
Geognostic and Geographic Situations.—Occurs imbedded in talc, and associated with lead-glaucite at Fahlun in Sweden.
3. Rhomboidal Corundum.—Jameson.
Rhombaedrischer Corund, Mohs.
Specific Character.—Rhomboidal. Rhomboid = . Cleavage . More perfect . Hardness = 9.0. Sp. gr. = 3.8, — 4.3.
Description.—Colours blue, red, grey, white, green, yellow, brown, and black. Occurs regularly cry-
stallized and massive. Lustre ranges from splendid Mineralogy. to glistening, and vitreous, or vitreous sometimes inclining to adamantine. Fracture conchoidal and uneven. Ranges from transparent to feebly translucent on the edges.
The transparent blue varieties are named sapphire; the transparent red varieties, oriental ruby; the massive, nearly opaque, grey and black varieties, emery; the translucent, massive, and crystallized varieties, common corundum; and the brown faintly translucent varieties, adamantine spar.
Geognostic and Geographic Situations.—The finest sapphires and oriental rubies are found in alluvial soil in Ceylon and Pegu, and other countries; the emery occurs in primitive talc-slate in Saxony; the common corundum and adamantine spar in granite, syenite, and other rocks in India and China.
4. Prismatic Corundum, or Chrysoberyl.—Jameson.
Prismatischer Corund, Mohs.—Krysoberyll, Werner.—Cymophane, Hauy.
Specific Character.—Prismatic. Pyramid = ; ; . . Cleavage = . Less perfect . (Fig. 29, 28.) Hardness = 8.5. Sp. gr. = 3.7, — 3.8.
Description.—Colour green, and often exhibits a milk-white opalescence. Occurs regularly crystallized, and in blunt edged pieces. Lustre splendid and resino-vitreous. Fracture conchoidal. Semi-transparent and transparent.
Geognostic and Geographic Situations.—Occurs imbedded in granite veins in America, and in alluvial soil in Ceylon.
Genus III.—DIAMOND.
Tessular. Hardness = 10. Sp. gr. = 3.4, — 3.6.
1. Octahedral Diamond.—Jameson.
Specific Character.—Tessular. Cleavage octahedral.
Description.—Its colours are more numerous than that of most other minerals, and of the various tints the grey and white are the most frequent; and it exhibits beautiful red, yellow, and blue varieties. Occurs regularly crystallized, and in roundish grains. The lustre splendid and adamantine. Fracture conchoidal. Transparent and semi-transparent.
Geognostic and Geographic Situations.—It has hitherto been found principally loose in alluvial soil, in the warmer regions of the earth, as Brazil, Borneo, and the Peninsula of India.
Genus IV.—TOPAZ.
Prismatic. Cleavage axotomous. Hardness = 8. Sp. gr. = 3.4, — 3.6.
1. Prismatic Topaz.—Jameson.
Prismatischer Topaz, Mohs.—Topaz. Physalit. Piknit, Werner.—Silice Fluatée Alumineuse, Hauy.
Specific Character.—Prismatic. Pyramid = ; ; . . Combination, sometimes with different planes on opposite ends. Cleavage, . (Fig. 27.)
Description.—Colours yellow, green, blue, red,
Mineralogy. grey, white. Occurs regularly crystallized; also in prismatic and granular concretions, and massive. Lustre ranges from splendid to glistening, and is vitreous and resinous. Fracture conchoidal and uneven. Ranges from transparent to translucent on the edges. Easily and uncommonly easily frangible.
The highly crystallized and transparent varieties are named precious topaz; those in prismatic distinct concretions, with a slight degree of translucency on the edges, and which are uncommonly easily frangible, schorlous topaz; and those in coarse granular concretions, with a low degree of lustre, and feeble translucency on the edges, phytalite.
Geognostic and Geographic Situations.—Precious topaz occurs in alluvial soil in the upper parts of Aberdeenshire, and in primitive rocks in Cornwall; schorlous topaz is said also to occur in Aberdeenshire; and the phyalite in granite, at Finbo in Sweden.
Genus V.—EMERALD.
Rhomboidal. Prismatic. Cleavage rhomboid axotomous and peritomous, or prismatoidal. Hardness = 7.5, 8.0. Sp. gr. = 2.6, —3.2.
1. Prismatic Emerald, or Euclase—Jameson.
Euclase, Werner.—Prismatischer Smaragd, Mohs.—Euclase, Haüy.
Specific Character.—Prismatic. Pyramid unknown. . Combination, hemiprismatic. . Cleavage, . Very distinct.
Hardness = 7.5. Sp. gr. = 2.9, —3.2.
Description.—Colours green, white, and blue. Occurs regularly crystallized. Lustre splendid. Fracture conchoidal. Transparent and translucent. Very easily frangible.
Geognostic and Geographic Situations.—This beautiful and rare mineral has been hitherto found only in Peru and Brazil.
2. Rhomboidal Emerald—Jameson.
Rhomboidischer Smaragd, Mohs.—Emeraude, Haüy.
Specific Character.—Rhomboidal, . Combination di-rhomboidal. . Cleavage, . Less perfect, . Hardness = 7.5, —8.0. Sp. gr. = 2.6, —2.8.
Description.—Colours green, blue, yellow, and grey. Occurs regularly crystallized, and in thin prismatic concretions. Lateral planes longitudinally streaked or smooth. Lustre ranges from splendid to glistening, and is vitreous. Fracture conchoidal. Ranges from transparent to translucent on the edges. Easily frangible.
The varieties, with emerald-green colours, and, in short, smooth, transparent, and translucent prisms, with rough terminal planes, are named precious emerald, while the others, in which the colours are green, blue, yellow, and grey, and crystallized in long longitudinally streaked prisms, are named beryl, or common emerald.
Geognostic and Geographic Situations.—The precious emerald is found in mica-slate, and clay-slate,
and the finest varieties are those imported from Peru. The beryl, or common emerald, occurs in Aberdeenshire; but nearly all the varieties, met with in trade, are brought from Russia.
Genus VI.—QUARTZ.
Rhomboidal, prismatic. Cleavage not axotomous. Hardness = 5.5, —7.5. Sp. gr. = 1.9, —2.7.
1. Prismatic Quartz, or Iolite—Jameson.
Prismatischer Quarz, Mohs.—Iolithe. Peliom, Werner.—Iolithe, Haüy.—Dichroite. Steinheilite, Auct.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, (nearly). (Fig. 30, 29.) Hardness = 7.0, —7.5. Sp. gr. = 2.5, —2.6.
Description.—Colour blue. Of an indigo blue colour, when viewed in the direction of the axis, but viewed perpendicular to the axis, is brownish yellow. Occurs rarely crystallized, generally massive and disseminated. Lustre shining and vitreous. Fracture uneven and conchoidal. Translucent in the direction of the axis, and transparent at right-angles to it.
Geognostic and Geographic Situations.—Occurs in granite, gneiss, and it is said also in volcanic tuffa; also in Finland, Arendal in Norway, St Gothard in Switzerland, and Granatillo in Spain, are localities of this mineral.
2. Rhomboidal Quartz—Jameson.
Quarz, Werner.—Rhomboidischer Quarz, Mohs. Specific Character.—Rhomboidal. Rhomboid = . Combination, hemi-rhomboidal and hemi-
dirhomboidal. and , with inclined planes, and with parallel planes. Cleavage, . . Hardness = 7.0. Sp. gr. = 2.5, —2.7.
Description.—Colours white, grey, rarely black, blue, green, yellow, red, and brown. Occurs regularly crystallized; in granular, fibrous, prismatic, and lamellar concretions; also massive, disseminated, in plates, stalactitic, reniform, botryoidal, globular, specular, vesicular, and cellular. Lustre ranges from splendid to glistening, and is vitreous. Fracture conchoidal, even, uneven, and splintery. Ranges from transparent to opaque. Brittle, and easily frangible.
The transparent and highly crystallized varieties are named rock crystal. The pyramidal, translucent, and transparent varieties, having generally a violet blue colour, and disposed in prismatic, fibrous, and lamellar concretions, are named amethyst. The massive, strongly translucent, rose-red, and milk-white varieties, are named rose quartz. Those varieties which have generally grey or white colours, the pyramidal form, and occur massive, disseminated, and in the various particular external forms enumerated above, with a low degree of lustre and translucency, are named common quartz. The leek-green translucent varieties, with a resinous-vitreous lustre, and conchoidal-splintery fracture, are named prase. The cat's eye is a variety, with a beautiful opalescence, like the light of the eye of the cat. Those opaque varieties, in which the colours are red, brown, and yellow, and the lustre shining externally, and glist-
Mineralogy.—Opening internally, and vitreo-resinous, and fracture small conchoidal, are named iron-flint. Those varieties which exhibit grey, yellow, brown, red, and green, generally muddy colours, and which occur massive and in extraneous external shapes, with a splintery, or conchoidal, and dull, or glistening fracture, and are opaque or translucent on the edges, are named horn-stone. The grey, brown, and black varieties which generally occur massive, and in various particular and extraneous external forms, and exhibit a glistening lustre, conchoidal fracture, and feeble translucency, are named flint. The semi-transparent and translucent varieties, in massive and various particular external forms, with an even and dull fracture surface, are named common calcedony. The beautiful apple-green strongly translucent varieties are named chrysoprase. The grass-green varieties, with glistening lustre, conchoidal fracture, and strong translucency, are named plasma. The semi-transparent and strongly translucent varieties, with glistening or shining vitreous lustre and conchoidal fracture, and with various tints of red, brown, yellow, green, and white, are named carnelian. The beautiful variety, named heliotrope, is well characterized, on a general view, by its green colour, and disseminated spots of red and yellow jasper. Those varieties, in which the colours are red, brown, and black, and seldom yellow or green, which occur massive and disseminated, with a fracture ranging from conchoidal to earthy, and lustre from glistening to dull, and are opaque, are named jasper. And, lastly, the white and grey varieties, which are so porous and light, as to swim on the surface of water, are named spongiform quartz, or floatstone.
Geognostic and Geographic Situations.—Quartz is very universally distributed, and, as far as we know at present, is the most abundant mineral in nature. It occurs in every rock, from granite to the newest secondary formation; and every country, every district in the world, afford examples of this mineral.
3. Uncleavable Quartz.—Jameson.
Untheilbarer Quartz, Mohs.
Specific Character.—Reniform....Massive. No cleavage. Hardness =5.5, —6.5. Sp. gr. =1.9, —2.2.
Description.—Colours white and grey, also green, yellow, brown, red, and black, and sometimes displays a beautiful play of colour. Occurs massive, and in various particular external forms. Lustre ranges from splendid to glistening, and is vitreous, or vitreo-resinous. Ranges from transparent to opaque.
The grey and white varieties, with glistening and shining pearly lustre, and translucent on the edges, or translucent in the mass, are named quartz sinter, or pearl sinter. The yellowish and greyish white varieties with the botryoidal and other particular external forms, conchoidal fracture and vitreous lustre, and which are strongly translucent, are named hyalite. The milk-white varieties, with the beautiful play of various rich and pure colours, are named precious opal. The transparent varieties, with the beautiful carmine-red and apple-green iridescence, are named fire opal. Those varieties which are milk-white, and frequently dendritic, with a pearly, shining, or glistening lustre,
conchoidal fracture, and complete opacity, are named mother-of-pearl opal, or cacholong. The common opal differs from the precious, principally in wanting the play of colour. The feeble translucent varieties, with conchoidal fracture, and glistening vitreo-resinous lustre, and white, grey, and brown colours, are named semi-opal. Those varieties, in which the colours are red, yellow, and grey, with a shining vitreo-resinous lustre, conchoidal fracture, and opacity, are named jasper-opal. Those varieties which occur in various vegetable forms, and are really vegetables impregnated, or petrified with opal, are named wood-opal. And, lastly, the brown and yellowish grey tuberose varieties are named menilite.
Geognostic and Geographic Situations.—This species has a comparatively limited geognostic and geographic distribution. The quartz sinter occurs in the vicinity of hot-springs, as in Iceland and other countries; the hyalite in secondary trap-rocks in Scotland, Germany; and the various opals are found principally in secondary trap, and in porphyry rocks in Hungary, Germany, Scotland, and other countries.
4. Fusible Quartz.—Jameson.
Empyrox Quartz, Mohs.
Specific Character.—In grains....Massive. No cleavage. Hardness =6.0, —7.0. Sp. gr. =2.2, —2.4.
Description.—Colours black, green, and grey; also brown, blue, red, yellow, and white. Occurs in globular, lamellar, and prismatic concretions; massive, vesicular, and porous. Lustre ranges from splendid to glistening, and is vitreous, resinous, and pearly. Ranges from transparent to opaque.
The varieties, with splendid and vitreous lustre, conchoidal fracture, and ranging from transparent to translucent on the edges, are named obsidian; those again in which the lustre is shining and resinous, and translucent on the edges, are named pitchstone; the beautiful varieties in globular and concentric lamellar, shining, pearly, translucent concretions, are named pearlstone; and lastly, the white and grey varieties, which are vesicular and fibrous, with a vitreous or pearly lustre, and often so light as to swim on water, are named pumice.
Geognostic and Geographic Situations.—All the minerals of this series are, by some, said to be of volcanic origin, by others to have a double origin, in some cases being volcanic, in others of Neptunian formation. The pitchstone abounds in Scotland, in the Island of Arran, also in the Isle of Egg, in Rum, Skye, and other quarters; pearlstone occurs in great beauty in Hungary and Iceland, and both pumice and obsidian are productions of Iceland, the Lipari Islands, and of other districts, said to be of volcanic origin.
Genus VII.—AXINITE.
Perfect vitreous lustre. Hardness =6.5, —7.0. Specific gravity =3.0, —3.3.
1. Prismatic Axinite.—Jameson.
Prismatischer Axinit, Mohs.—Thumerstein, Werner.—Axinite, Haug.
Specific Character.—Prismatic. Pyramid unknown.
Mineralogy. Combination, tetarto-prismatic. Cleavage, two faces, the one more distinct than the other. Incidence = .
Description.—Colours brown, blue, and sometimes grey and black. Occurs regularly crystallized; in curved lamellar concretions, and massive. Lustre externally splendid, internally glistening, or shining, and vitreous. Ranges from transparent to feebly translucent. Brittle, and very easily frangible.
Geognostic and Geographic Situations.—Occurs in beds and veins in gneiss, mica-slate, clay-state, and hornblende-slate. It occurs in small quantities in Cornwall, but no where else in Great Britain.
Genus VIII.—CHRY SOLITE.
Perfect vitreous lustre. Hardness = 6.5, —7.0. Sp. gr. = 3.3, —3.5.
1. Prismatic Chrysolute.—Jameson.
Prismatischer Krisolith, Mohs.—Peridot, Häuy.
Specific Character.—Prismatic. Pyramid = ; ; . . Cleavage, . Less distinct . (Fig. 29, 28.)
Description.—Colour green. Occurs regularly crystallized. Lustre splendid and vitreous. Fracture conchoidal. Transparent.
The varieties in granular distinct concretions, and which have a lower degree of transparency and lustre than the more highly crystallized kinds, are those generally described under the name olivine.
Geognostic and Geographic Situations.—The mineral occurs principally in secondary trap-rocks, and in alluvial strata. The olivine variety is not unfrequent in some of the middle and western districts of Scotland. The chrysolites of commerce are brought from the Brazils and Upper Egypt.
Genus IX.—BORACITE.
Tessular. Hardness = 7. Sp. gr. = 2.8, —3.0.
1. Octahedral Boracite.—Jameson.
Octaedrischer Borazit, Mohs.—Borazit, Werner.—Magnesie Boratée, Häuy.
Specific Character.—Tessular. Combination, semi-tessular of inclined planes. Cleavage, imperfect.
Description.—Colours white and grey. Occurs regularly crystallized. Internally shining and adamantine. Fracture conchoidal. Translucent and transparent.
Genus X.—TOURMALINE.
Rhomboidal. Hardness = 7.0, —7.5. Sp. gr. = 3.0, —3.2.
1. Rhomboidal Tourmaline.—Jameson.
Rhomboedrischer Turmaline, Mohs.—Tourmaline, Häuy.
Specific Character.—Rhomboidal. Rhomboid = . Combination, with different planes on opposite extremities. Cleavage, .
Description.—Colours black, brown, green, blue,
red, and white. Occurs regularly crystallized; in prismatic and granular distinct concretions, massive and disseminated. Lustre ranges from splendid to glistening, and is vitreous. Fracture conchoidal and uneven. Ranges from transparent to opaque. Brittle and easily frangible.
The black coloured opaque varieties, with uneven fracture, are named schorl; all the others are ranged under the title tourmaline.
Geognostic and Geographic Situations.—It occurs imbedded in granite, gneiss, mica-slate, talc-slate, chlorite slate, dolomite, topaz-rock, and quartz-rock; also in felspar, mica, talc, &c. and in alluvial strata. The schorl varieties occur in various primitive rocks in the Alpine districts of Scotland, and the purer varieties, or tourmaline, properly so called, are met with in Siberia, Spain, and many other countries.
Genus XI.—GARNET.
Tessular, pyramidal, prismatic. Lustre not pure vitreous. Hardness = 6.0, —7.5. Sp. gr. = 3.0, —4.3. If colour red, the sp. gr. = 3.7, and more. If black, sp. gr. = 3.9, and less. If hardness, 7.5, the colour is red or brown.
1. Pyramidal Garnet, or Vesuvian.—Jameson.
Pyramidal Granat, Mohs.—Vesuvian, and Egeran, Werner.—Idocrase, Häuy.
Specific Character.—Pyramidal. Pyramid = ; . Cleavage, . . . Hardness = 6.5. Sp. gr. = 3.3, —3.4.
Description.—Colours green and brown, and rarely blue. Occurs regularly crystallized; in granular distinct concretions, massive, and disseminated. Externally splendid, and internally feebly shining and vitreous. Fracture uneven, inclining to small conchoidal. Ranges from transparent to translucent in the edges.
Geognostic and Geographic Situations.—Occurs in primitive rocks in Ireland, also in Scotland; and on the continent of Europe the most beautiful varieties are there found in the unaltered ejected masses in Somma, near Naples, where they are associated with granular limestone, garnet, hornblende, mica, chlorite, augite, meionite, nepheline, magnetic iron-ore, &c.
2. Tetrahedral Garnet, or Helvine.—Jameson.
Helvin, Werner.—Tetraedrischer Granat, Mohs.
Specific Character.—Tessular. Combination, semi-tessular of inclined planes. Cleavage, octahedral, but imperfect. Hardness = 6.0, —6.5. Sp. gr. = 3.1, —3.3.
Description.—Colours yellow, green, and brown. Occurs regularly crystallized, and in granular distinct concretions. Lustre ranges from splendid to glistening and vitreous. Fracture uneven. Translucent.
Geognostic and Geographic Situations.—Occurs in a bed in gneiss, associated with fluor-spar, slate-spar, chlorite, quartz, blende, and copper-pyrites, near Schwarzenberg, in Saxony.
3. Dodecahedral Garnet.—Jameson.
Specific Character.—Tessular. Cleavage dodeca-
Mineralogy: hedral imperfect. Hardness = 6.5, — 7.5. Sp. gr. = 3.5, — 4.3.
Description.—Colours red, brown, green, black, grey, and yellow. Occurs regularly crystallized; in angulo-granular concretions, and massive. Lustre ranges from splendid to glimmering, and is vitreous inclining to resinous, resino-vitreous, and resino-adamantine. Fracture conchoidal, splintery, uneven. Ranges from transparent to opaque.
The asparagus-green varieties in leucite formed crystals are named grossularie; the greyish-black dodecahedral opaque varieties, which externally have a metallic-like aspect, pyreneite; the velvet-black, dodecahedral, opaque varieties, melanite; the green, brown, and grey massive varieties, with glimmering lustre, and feeble translucency on the edges, allochroite; the brown and red varieties in granular concretions, with resino-adamantine lustre, colophonite; the red highly crystallized transparent varieties, precious garnet; the yellow nearly transparent varieties topazolite or yellow garnet; the brown and green varieties, in crystals often rounded on the edges, in granular concretions, and translucent, or translucent on the edges, common garnet; and lastly, the deep blood-red variety in roundish and angular grains, and completely transparent, pyrope.
Geognostic and Geographic Situations.—This mineral occurs principally in primitive rocks, either disseminated through them, or forming any ingredient in the composition of subordinate beds; it is comparatively rare in transition rocks, and is still less frequently met with in secondary formations. In Scotland the precious garnet is common in several Highland districts in Perthshire, Aberdeenshire, &c.; and the pyrope variety occurs in secondary trap-rocks in Fife-shire.
4. Prismatic Garnet, or Cinnamon-Stone.—Jameson.
Prismatischer Garnet, Mohs.—Kaneelstein, Werner.—Essonite, Hauy.
Specific Character.—Prismatic. (Fig. 30.) Pyramid unknown. Cleavage, , indistinct. Hardness = 7.0, — 7.5. Sp. gr. = 3.5, — 3.7.
Description.—Colour intermediate between hyacinth-red and orange-yellow. Occurs in granular distinct concretions, and massive. Lustre shining and resino-vitreous. Fracture conchoidal. Transparent and translucent.
Geognostic and Geographic Situations.—Occurs in gneiss in Kincardineshire; the finer varieties are imported from Ceylon, where they are found in the beds of rivers, and also associated with gneiss.
5. Prismatoidal Garnet, or Grenatite.—Jameson.
Prismatoidischer Granat, Mohs.—Granatit, Werner.—Staurotide, Hauy.
Specific Character.—Prismatic. Pyramid = ; ; . . Cleavage, , perfect. (Fig. 29.) Hardness = 7.0, — 7.5. Sp. gr. = 3.3, — 3.9.
Description.—Colour reddish brown. Occurs regularly crystallized. Internally the cleavage is shining and splendid; fracture glistening and glimmering,
and resino-vitreous. Fracture uneven. Ranges from semi-transparent to opaque. Mineralogy.
Geognostic and Geographic Situations.—Occurs in primitive rocks in the Shetland Islands and in Aberdeenshire, and other parts of Scotland.
* Aplome.—Colour dark brown. Tessular. Cleavage, hexahedral. Hardness = 7. Sp. gr. = 3.446.
** Eudialite.—Colour brownish red. Rhombohedral, . Cleavage, . Less distinct, . Hardness = 5.0, — 5.5. Sp. gr. = 2.8, — 3.0. Its native country is West Greenland.
Genus XII.—ZIRCON.
Pyramidal. Hardness = 7.5. Sp. gr. = 4.5, — 4.7.
1. Pyramidal Zircon.—Jameson.
Pyramidal Zircon, Mohs.
Specific Character.—Pyramidal. Pyramid = ; . Cleavage, .
Description.—Colours grey and hyacinth red; also white, green, brown, and rarely yellow, blue, and red. Occurs regularly crystallized. Lustre splendid, shining, and adamantine-resinous and resino-vitreous. Fracture conchoidal. Ranges from transparent to opaque.
Those varieties in which the cleavage is very distinct, and which have frequently a hyacinth red colour, are named hyacinth, the other varieties common zircon.
Geognostic and Geographic Situations.—Occurs in syenite, granite, gneiss, primitive trap, in secondary trap, and unaltered ejected masses of Somma. The syenite rocks of Galloway, the gneiss rocks of Inverness-shire and of the Shetland Islands, afford examples of this mineral.
Genus XIII.—GADOLINITE.
Prismatic. Colour black. Hardness = 6.5, — 7.0. Sp. gr. = 4.0, — 4.3.
1. Prismatic Gadolinite.—Jameson.
Prismatischer Gadolinit, Mohs.
Specific Character.—Prismatic. Pyramid unknown. (nearly). Combination, hemiprismatic.
Description.—Colour black, and rarely hyacinth red. Occurs in granular and prismatic concretions, and massive. Internally shining, and lustre, resino-vitreous. Fracture conchoidal, seldom uneven. Opaque.
Geognostic and Geographic Situations.—Occurs in beds of felspar, in mica-slate at Ytterby, and in granite at Finbo, in Sweden.
Order VIII.—ORE.
Hardness = 2.5, — 7. Sp. gr. = 3.4, — 7.4. If the lustre is metallic, the colour is black. If the lustre is not metallic, it is adamantine or imperfect, or semi-metallic lustre. If the streak is yellow or red, the hardness = 3.5, and more, and the sp. gr. = 4.8, and more. If the streak is brown or black, the hardness = 5.0, and more, or the cleavage montomous. If the hardness = 4.5, and less, the streak is yellow, red, or black. If hardness = 6.5, and more, the streak is white or grey, and the sp. gr. = 6.5, and more.
Pyramidal, prismatic. Hardness =5.0, —6.5. Sp. gr. =3.4, —4.4. If sp. gr. less than 4.2, the streak is white or grey.
1. Prismatic Titanium-Ore, or Sphene.—Jameson.
Prismatisches Titan-erz, Mohs.—Titane Siliceocalcaire, Haüy.
Specific Character.—Prismatic. Pyramid =111° 12'; 88° 47'; 131° 16'. . Combination, hemiprismatic. . Cleavage, . (Fig. 37.) Streak white or grey. Hardness = 5.0, —5.5. Sp. gr. =3.4, —3.6.
Description.—Colours brown, yellow, green, grey, and white. Occurs regularly crystallized; in granular and lamellar distinct concretions, and massive. Lustre ranges from splendid to glistening, and is adamantine. Fracture conchoidal. Ranges from transparent to opaque.
One set of varieties, in which brown is the predominating colour, is named common sphene, or brown titanium-ore; and another, in which the principal colours are yellow, and the cleavage distinct, is named yellow titanium-ore, or foliated sphene.
Geognostic and Geographic Situations.—This mineral occurs imbedded in syenite in Inverness-shire, Perthshire, Galloway, and many other quarters of Scotland; it also occurs in syenite rocks in England.
2. Perilomous Titanium-Ore, or Rutile.—Jameson.
Peritomes Titan-erz, Mohs.—Titan-oxydé, Haüy.—Rutil, Werner.
Specific Character.—Pyramidal. Pyramid =117° 2'; 95° 13'. Cleavage, . []. Streak brown. Hardness =6.0, —6.5. Sp. gr. =4.2, —4.4.
Description.—Colours brown, red, yellow, and sometimes nearly velvet black. Occurs regularly crystallized, massive, disseminated, in angular grains and in flakes. Lustre metallo-adamantine and adamantine, and ranges from splendid to glistening. Fracture conchoidal. Ranges from transparent to opaque.
The dark-brown and black opaque varieties are named nigrine; the others rutile.
Geognostic and Geographic Situations.—The rutile varieties occur in the granite of Cairngorm; at Killin, and in Ben-Gloe, in quartz rock. The nigrine varieties are met with at Ely, in Fifeshire, and also in Bohemia and Transylvania.
3. Pyramidal Titanium, or Octahedrite.—Jameson.
Pyramidales Titan-erz, Mohs.—Octaedrit, Werner.—Titane, Anatase, Haüy.
Specific Character.—Pyramidal. Pyramid =97° 38'; 137° 10'. Cleavage, . Streak white. Hardness =5.5, —6.0. Sp. gr. =3.8, —3.9.
Description.—Colours blue and brown. Occurs regularly crystallized. Lustre splendid and adamantine, inclining to semi-metallic. Translucent and transparent.
Geognostic and Geographic Situations.—Occurs in veins in primitive rocks in Saxony and in Norway.
Prismatic. Hardness =4.0, 4.5. Sp. gr. =6.2, —6.3.
1. Prismatic Zinc-Ore.—Jameson.
Specific Character.—Prismatic. Pyramid unknown. Cleavage (nearly). Traces of . (Fig. 30, 29.) Streak orange-yellow.
Description.—Colour red. Occurs massive, and disseminated. Internally shining. Fracture conchoidal. Translucent on the edges, or opaque.
Geognostic and Geographic Situations.—Occurs imbedded in primitive limestone and magnetic iron-ore in Sussex county, and New Jersey, in North America.
Tessular. Hardness =3.5, —4.0. Sp. gr. =5.6, —6.0.
1. Octahedral Red Copper-Ore.—Jameson.
Octaedrisches Kupfererz, Mohs.—Roth Kupfererz, Werner.—Cuivre oxydulé, Haüy.
Specific Character.—Tessular. Cleavage octahedral. Streak red.
Description.—Colours red. Occurs regularly crystallized, and in granular distinct concretions; massive, disseminated, and in flakes. Lustre ranges from shining to glimmering, and is adamantine, inclining to semi-metallic. Fracture uneven. Ranges from translucent to opaque.
The varieties with cleavage are named foliated red copper-ore; those which are massive, glistening, and opaque, compact red copper-ore; and the varieties in capillary crystals, capillary red copper-ore.
Geognostic and Geographic Situations.—Occurs in veins in gneiss, mica-slate, clay-slate, and grey-wacke; and in veins and beds in secondary rocks. The copper mines of Cornwall afford fine examples of this beautiful ore.
Zinnerz, Mohs.
Pyramidal. Streak not black. Hardness =6.0, —7.0. Sp. gr. =6.3, —7.0.
1. Pyramidal Tin-Ore.—Jameson.
Pyramidales Zinnerz, Mohs.
Specific Character.—Pyramidal. Pyramid =135° 25'; 67° 59'. Cleavage . []. Streak white, grey, and brown.
Description.—Colours brown, black, green, white, yellow, and red. Occurs regularly crystallized; also reniform, botryoidal, and globular, and in delicate fibrous concretions. Externally splendid; internally ranges from splendid to glimmering, and is adamantine, inclining to resinous. Fracture uneven. Ranges from semi-transparent to opaque.
The varieties in fibrous concretions are named wood-tin, the others common tin-stone.
Geognostic and Geographic Situations.—Occurs in granite, gneiss, mica-slate, clay-slate, porphyry, and in alluvial depositions. The mines of Cornwall afford all its varieties.
Mineralogy. beds, often of vast thickness and great extent, in rocks of the older formations, as gneiss, mica-slate, hornblende-slate, clay-slate, and primitive greenstone, variously disposed in granite, syenite, serpentine, and chlorite-slate; less frequently in transition rocks, in veins, beds, and imbedded masses, as in transition porphyry; and still less frequently in secondary trap-rocks. The serpentine, chlorite, and gneiss rocks of the Shetland Islands afford examples of this ore; the same is the case on the Mainland of Scotland, both in primitive and secondary rocks.
2. Rhomboidal Iron-Ore.—Jameson.
Rhomboedrisches Eisen-erz, Mohs.—Fer oligiste, Haüy.
Specific Character.—Rhomboidal. Rhomboid = . Cleavage R. Sometimes R = . Streak red, reddish-brown. Hardness = 5.5, —6.5. Sp. gr. = 4.8, —5.2.
Description.—Colours dark steel-grey bordering on iron-black, iron-black and brownish-red. Occurs regularly crystallized; in granular, lamellar, and fibrous distinct concretions; massive, disseminated, reniform, botryoidal, stalactitic, and globular. Lustre ranges from splendid to dull, and is metallic and semi-metallic. Fracture conchoidal or earthy. Ranges from translucent to opaque.
The dark steel-grey and iron-black varieties, which are generally more or less regularly crystallized, are named specular iron-ore, or iron-glance; the red varieties are named red iron-ore.
Geognostic and Geographic Situations.—The specular iron-ore occurs in gneiss, granite, mica-slate, transition clay-slate, greywacke, and less frequently in secondary rocks. The Island of Elba affords the richest and most beautiful varieties of specular iron-ore, and specimens of considerable beauty are met with in Fitful-head in Shetland, and near Dunkeld in Perthshire. The red iron-ore occurs also in primitive rocks, but less frequently than in those of the transition class, as greywacke and transition clay-slate; and considerable depositions of it are met with in secondary sandstone districts. Ulverstone in Lancashire and other parts of England afford beds and veins of this ore.
3. Prismatic Iron-Ore.—Jameson.
Prismatisches Eisen-erz, Mohs.—Braun Eisenstein, Werner.—Fer oxydé, Haüy.—Fer Hydraté, Daubuisson.
Specific Character.—Prismatic. Pyramid unknown. Cleavage prismatic. Streak yellowish-brown. Hardness = 5.0, —5.5. Sp. gr. = 3.8, —4.2.
Description.—Colours brown and yellow. Occurs regularly crystallized; in granular, fibrous, and lamellar distinct concretions; massive, stalactitic, coralloidal, reniform, botryoidal, tuberculate, cylindrical, and fruticose. Lustre glimmering and semi-metallic, inclining more or less to adamantine. Fracture uneven, even, conchoidal, or earthy. Translucent on the edges, or opaque.
Geognostic and Geographic Situations.—Occurs in veins, beds, lenticular masses, and mountain masses, in primitive, transition, and secondary rocks in Great Britain, Germany, and other countries.
* Bog Iron-Ore.—Jameson.
Raseneisenstein, Werner.
Description.—Colour brown. Occurs massive, vesicular, corroded, amorphous, and tuberculate. Some varieties are friable. Lustre ranges from glistening to dull, and is semi-metallic-resinous. Fracture earthy or conchoidal. Opaque. Yields a yellowish-grey streak. Brittle, and easily frangible. Sp. gr. = 2.944.
Geognostic and Geographic Situations.—It occurs in alluvial soil and in peat-mosses in various places of Scotland, and in the Orkney, Shetland, and Western Islands.
** Lievrite. Ienite. Ilvaite.
Fer Siliceo-calcaire, Haüy.
Specific Character.—Prismatic. Pyramid = ; ; . Cleavage Pr = . P + = . Pr + . None distinct. Colour black. Streak black, inclining sometimes to green or brown. Hardness = 5.5, —6.0. Sp. gr. = 3.825, —4.061.
Description.—Colour black, blackish green. Occurs regularly crystallized; also in distinct concretions, which are scopiform radiated, or straight radiated. Lustre glistening and semi-metallic. Fracture uneven. Opaque.
Geognostic and Geographic Situations.—Occurs associated with epidote, garnet, magnetic iron ore, and arsenic pyrites, in limestone, in the Island of Elba; and has been found in Norway and West Greenland.
Genus XI.—MANGANESE-ORE.
Mangan-erz, Mohs.
Prismatic. Hardness = 2.5, —6.0. Sp. gr. = 4.3, —4.8.
1. Prismatic Manganese-Ore, or Black Manganese-Ore.—Jameson.
Prismatisches Mangan-erz, Mohs.—Schwarzer Braunstein and Schwarz-eisenstein, Werner.—Manganese oxydé, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage unknown, imperfect. Streak black, inclining to brown. Hardness = 5.0, —6.0.
Description.—Colours black and steel-grey. Occurs regularly crystallized; also in fibrous and lamellar distinct concretions; massive, tuberculate, fruticose, reniform, and botryoidal. Lustre glimmering, glistening, and imperfect metallic. Fracture conchoidal and uneven. Opaque.
Geognostic and Geographic Situations.—Occurs in veins in primitive, transition, and secondary rocks in Hanover, Saxony, &c.
* Scaly Brown Manganese-Ore.—Jameson.
Brauner Eisenrahm, Werner.
Description.—Colour between steel-grey and clove-brown. Occurs in crusts, massive, spumous, fruticose, and irregular dendritic. Friable, or friable passing into soft. Composed of scaly particles, which are glistening and metallic. Soils. Feels greasy. Occurs in the mines of Sandlodge, in Shetland.
Prismatoidisches mangan-erz, Mohs.—Graubraunsteinerz, Werner.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, . = 100° (nearly). More distinct, . (Fig. 30, 29.) Streak black. Hardness = 2.5, — 3.0.
Description.—Colour dark steel-grey, inclining to iron-black. Occurs regularly crystallized; in granular, fibrous, and radiated distinct concretions. Lustre shining, glimmering, and metallic. Fracture conchoidal and earthy.
Geognostic and Geographic Situations.—Occurs in veins and imbedded masses in primitive, transition, and secondary rocks. In Aberdeenshire, it occurs in primitive rocks; in Devonshire, in the vicinity of those of the transition class; and in Cornwall, it is associated with clay-slate.
Colours grey and brown. Occurs massive, botryoidal, and sometimes pulverulent. Internally dull, but the grey varieties are glimmering. Yields to the nail. It occurs along with the grey manganese-ore in Devonshire and Cornwall.
Pitchy Iron-ore, Werner.—Manganese Phosphat, Haüy.
Colour between pitch-black and clove-brown. Occurs massive, and crystallized in oblique prisms. Cleavage, three perpendicular faces, of which one is less perfect than the others. Lustre glistening and resinous. Fracture conchoidal, inclining to even and uneven. Translucent on the edges. Streak yellowish-grey, and brown. Hardness = 5.0, — 5.5. Sp. gr. = 3.430, Vauquelin. 3.775, Ullman. Occurs in disseminated masses in granite near Limoges, in France.
Lustre metallic. Not black. Hardness = 0...5. Sp. gr. = 5.7, — 20. If grey, it is malleable, and the sp. gr. = 7.4, and more. If the hardness = 4.0, it is malleable.
Form unknown. Tin-white, inclining to lead-grey. Hardness = 3.5. Sp. gr. = 5.7, — 5.8.
Gediegen Arsenik, Werner and Mohs.—Arsenic natif, Haüy.
Specific Character.—Regular form unknown. Cleavage unknown.
Description.—Colour tin-white, which soon tarnishes black on exposure. Occurs massive, in plates, reniform, botryoidal, reticulated, and with impressions. Lustre glistening, glimmering, and metallic. Fracture uneven. Emits, when struck, a ringing sound, and an arsenical odour.
Geognostic and Geographic Situations.—It occurs in metalliferous veins, particularly where they cross
each other, in gneiss, mica-slate, clay-slate, and porphyry; seldom in transition and secondary rocks; rarely in beds, and never in large quantity. The mines of Germany, Norway, France, and Russia, afford examples of this mineral. Mineralogy.
Form unknown. Tin-white. Hardness = 2.0, — 2.5. Sp. gr. = 6.1, — 6.2.
Gediegenes Tellur, Mohs.—Gediegen Sylvan, Werner.—Tellur natif, Haüy.
Specific Character.—Regular form unknown. Cleavage unknown.
Description.—Colour tin-white. Occurs in granular distinct concretions, massive, and disseminated. Lustre shining and metallic. Rather brittle, and easily frangible.
Geognostic and Geographic Situations.—Occurs in greywacke, in Transylvania, and also in Tellemark, in Norway.
Tessular, prismatic. Not ductile. White. Hardness = 3.0, — 3.5. Sp. gr. = 6.5, — 10.0.
Dodecaedrisches Antimon, Mohs.—Gediegen Spiesglas, Werner.—Antimoine natif, Haüy.
Specific Character.—Tessular. Cleavage octahedral. Dodecahedral.
Description.—Colour tin-white. Occurs regularly crystallized; in granular and lamellar concretions; massive, disseminated, and reniform. Lustre splendid and metallic.
Geognostic and Geographic Situations.—Occurs in metalliferous veins in primitive rocks in Sweden, and in the mountains of Hanover, Dauphiny, Hungary, and Brazil.
Prismatisches Antimon, Mohs.—Spiesglas Silber, Werner.—Argent Antimonial, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, . Pr. Less distinct, . (Fig. 27, 34, 30.) Hardness = 3.5. Sp. gr. = 8.9, — 10.0.
Description.—Colour between silver and tin-white. Occurs regularly crystallized, and massive. Lustre splendid and metallic. Sectile.
Geognostic and Geographic Situations.—Occurs in veins in primitive and transition rocks in Furstenberg, Salzburg, Hartz, and Spain.
Tessular. Silver-white, inclining to red. Hardness = 2.0, — 2.5. Sp. gr. = 8.5, — 9.0.
Octaedrisches Wismuth, Mohs.—Gediegen Wismuth, Werner.—Bismuth natif, Haüy.
Specific Character.—Tessular. Cleavage, octahedral.
Mineralogy. Description.—Colour silver-white. Occurs regularly crystallized; massive, disseminated, dentiform, and in leaves with a plumose streaked surface. Lustre splendid and metallic. Malleable.
Geognostic and Geographic Situations.—Occurs in veins in primitive rocks, as gneiss, granite, mica-slate, and clay-slate, in Cornwall, Germany, France, Norway, &c.
Genus V.—MERCURY.
Tessular, liquid. Not malleable. White. Hardness = 0.0, —3.0. Sp. gr. = 10.5, —15.0.
1. Liquid Native Mercury.—Jameson.
Flüssiges Mercur, Mohs.—Gediegen Quecksilber, Werner.—Mercur Nativ, Haüy.
Specific Character.—Liquid. Tin-white. Hardness = 0. Sp. gr. = 12.0, —15.0.
Description.—Colour tin-white. Liquid. Splendent and metallic. Opaque.
Geognostic and Geographic Situations.—Rarely in primitive and transition rocks. More frequently in rocks of the coal formation. Deux-Ponts, Idria, and other European mining districts, afford examples of this metal.
2. Dodecahedral Mercury, or Native Amalgam.—Jameson.
Dodecaedrisches Mercur, Mohs.—Natürlich Amalgam, Werner.—Mercur Argential, Haüy.
Specific Character.—Tessular. No cleavage. Silver-white. Hardness = 1.0, —3.0. Sp. gr. = 10.5, —12.5.
Description.—Colour silver-white. Occurs regularly crystallized. Lustre shining and metallic. Fracture uneven. When pressed between the fingers, or cut with a knife, it emits a creaking sound, like artificial amalgam.
Geognostic and Geographic Situations.—Occurs in Deux-Ponts, and other mercury mines, along with cinnabar.
Genus VI.—SILVER.
Tessular. Ductile. Silver-white. Hardness = 2.5, —3.0. Sp. gr. 10.0, —10.5.
1. Hexahedral Silver.—Jameson.
Hexaedrisches Silber, Mohs.—Argent Nativ, Haüy.
Specific Character.—Tessular. No cleavage.
Description.—Colour silver-white, and silver-white inclining to brass-yellow. Occurs regularly crystallized, massive, disseminated, dentiform, filiform, reticulated, and in leaves. Lustre metallic, and ranges from splendent to glimmering. Fracture hackly, Opaque.
The yellow varieties are named auriferous native silver, from their containing a portion of gold; the other varieties common native silver.
Geognostic and Geographic Situations.—Common native silver occurs in veins, generally occupying their middle or upper parts; and those veins traverse granite, gneiss, mica-slate, clay-slate, hornblende-slate, syenite, and porphyry in primitive mountains, and greywacke in transition mountains. It rarely occurs in secondary rocks, as in sandstone. The mines of Cornwall, Saxony, Hungary, Mexico, afford this mi-
neral in all its forms. The auriferous native silver Mineralogy. was formerly found in the mines of Königsberg in Norway; and, at present, in those of Schlangenberg in Siberia.
Genus VII.—GOLD.
Tessular. Yellow. Hardness = 2.0, —2.5. Sp. gr. = 12.0, —20.0.
1. Hexahedral Gold.—Jameson.
Hexaedrisches Gediegen Gold, Mohs.—Gediegen Gold, Werner.—Or Nativ, Haüy.
Specific Character.—Tessular. No cleavage.
Description.—Colours gold-yellow and brass-yellow. Occurs regularly crystallized, massive, disseminated, in flakes, in leaves, reticulated, capillary, dentiform, and in grains. Lustre shining, glistening, and metallic. Fracture hackly. Opaque.
The gold-yellow varieties are named gold-yellow gold; the brass-yellow varieties, brass-yellow gold; those varieties, in which the brass-yellow verges on steel-grey, are named greyish-yellow gold; and, lastly, the pale brass-yellow, inclining to silver-white, varieties are named electrum, or argentiferous gold.
Geognostic and Geographic Situations.—Occurs in veins, and disseminated in granite, syenite, gneiss, mica-slate, hornblende-slate, porphyry, greywacke, clay-slate, &c.; also in various alluvial deposits. The mines of Germany, Hungary, and America, afford examples of the various mineralogical and geological relations of this important mineral.
Genus VIII.—PLATINA.
Form unknown. Steel-grey. Hardness = 4.0, —4.5. Sp. gr. = 16.0, —20.0.
1. Native Platina.—Jameson.
Gediegen Platin, Werner, Mohs.—Platin Nativ, Haüy.
Specific Character.—Form unknown. No Cleavage.
Description.—Colour pale steel-grey, approaching to silver-white. Occurs in flat grains and rolled pieces. Lustre shining and metallic.
Geognostic and Geographic Situations.—Occurs in alluvial soil, along with grains and loose crystals of chrome-ore, magnetic iron-ore, iron and copper pyrites, osmium, iridium, zircon, spinel, quartz, and native gold, in New Grenada, and Brazil in South America.
* Osmium-Iridium.—Colour steel-grey, slightly inclining to silver-white. Occurs in six-sided prisms, and in grains. Lustre shining and metallic. Harder than platina. Not malleable. Sp. gr. = 19.5.
Geognostic and Geographic Situations.—Occurs in the same districts in South America, and in the same alluvial formation as affords the platina.
** Native Palladium.—Colour steel-grey, inclining to silver-white. Occurs in loose grains. Lustre shining and metallic. Sp. gr. = 11.8, —12.14.
Geognostic and Geographic Situations.—Occurs along with platina in alluvial districts in Brazil.
Genus IX.—IRON.
Tessular. Pale steel-grey. Hardness 4.5. Sp. gr. = 7.4, —7.8.
Octaedrisches Eisen, Mohs.—Gediegen Eisen, Werner.—Fer Natif, Haüy.
Specific Character.—Tessular. No cleavage.
Description.—Colour pale steel-grey. Occurs ramosely, and disseminated in meteoric stones. Lustre glimmering, glistening, and metallic. Fracture hackly.
Geographic Situation.—It is a meteoric production, and has been observed to fall from fireballs in Europe, Asia, and America.
N.B.—Native iron is mentioned as having been met with imbedded in graphite in the State of New York in America, and in metallic sulphurets in South America; and native steel is enumerated amongst the pseudo-volcanic productions of the department of Allier in France.
Tessular. Copper-red. Hardness = 2.5, —3.0. Sp. gr. = 8.4, —8.9.
Octaedrisches Kupfer, Mohs.—Gediegen Kupfer, Werner.
Specific Character.—Tessular. No cleavage.
Description.—Colour copper-red. Occurs regularly crystallized; massive, dendritic, capillary, botryoidal, and ramosely. Lustre glistening and metallic. Fracture hackly.
Geognostic and Geographic Situations.—Occurs in granite, gneiss, mica-slate, clay-slate, primitive limestone, syenite, serpentine, greywacke, secondary limestone, sandstone, and generally in small veins; also in grains, and sometimes in blocks many pounds weight, in alluvial districts. It occurs in serpentine in Shetland, and in the copper mines of Cornwall. Large masses are met with in alluvial districts in the northern parts of North America.
Metallic lustre. Hardness = 3.5, —6.5. Sp. gr. = 4.1, —7.7. If hardness = 4.5, and less, the specific gravity is less than 5.0. If sp. gr. = 5.3, and less, the colour is yellow or red.
Prismatic. Hardness = 5.0, —5.5. Sp. gr. = 7.5, —7.7.
Prismatischer Nickel-kies, Mohs.—Kupfer-Nickel, Werner.—Nickel Arsenical, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage unknown. Copper-red.
Description.—Colour copper-red. Rarely crystallized; in granular distinct concretions; massive, disseminated, reticulated, dendritic, fruticose, globular, and botryoidal. Lustre shining and metallic. Fracture conchoidal. Brittle.
Geognostic and Geographic Situations.—Occurs in silver and cobalt veins in gneiss, mica-slate, clay-slate, and syenite; also in veins in secondary rocks, particularly bituminous marl-slate. In Scotland it is
met with at Leadhills and Wanlockhead, and in the coal-field of West Lothian.
Nickel Ochre.—Colour apple-green. Occurs as a thin coating, seldom massive, and disseminated. Dull. Fracture uneven or earthy. Opaque, or translucent on the edges. Soft. Feels meagre. It occurs in mineral veins along with copper-nickel at Alva in Stirlingshire, in Linlithgowshire, and at Leadhills.
Black Nickel.—Colour black. Occurs massive, disseminated, in crusts. Dull. Fracture earthy. Opaque. Soft. Shining in streak. Soils slightly. It occurs in veins in bituminous marl-slate at Riegelsdorf in Hesse.
Prismatic. Hardness = 5.0, —6.0. Sp. gr. = 5.7, —7.4. If white, the sp. gr. = 6.2, and less. If grey, the sp. gr. above 6.8.
Axentheilender Arsenik-kies, Mohs.—Arsenk-kies, Werner.
Specific Character.—Prismatic. Pyramid unknown. Cleavage . Less distinct . (Fig. 27, 30.) Pale steel-grey. Hardness = 5.0, —5.5. Sp. gr. = 6.9, —7.4.
Description.—Colour pale steel-grey. Occurs massive. Lustre metallic and shining.
Its locality unknown.
Prismatischer Arsenik-kies, Mohs.—Arsenk-kies, Werner.—Fer Arsenical, Haüy.
Specific Character.—Prismatic. Pyramid = ; ; . , . Cleavage . . (Fig. 27, 32.) White, inclining to steel-grey. Hardness = 5.5, —6.0. Sp. gr. = 5.7, —6.2.
Description.—Colour silver-white. Occurs regularly crystallized; in prismatic concretions, massive and disseminated. Lustre ranges from splendid to glistening, and is metallic. Fracture uneven. Opaque. Brittle.
Geognostic and Geographic Situations.—This mineral occurs in a variety of metalliferous formations in primitive mountains, and also in those of the transition and secondary classes. In Scotland it occurs in secondary rocks in Stirlingshire, and in considerable quantity in the mines of Devon and Cornwall.
Tessular. Hardness = 5.5. Sp. gr. = 6.0, —6.6.
Hexaedrischer Kobalt-kies, Mohs.—Glanz Kobold, Werner.—Cobalt gris, Haüy.
Specific Character.—Tessular. Combination semitessular of parallel planes. Cleavage hexahedral and perfect. White, inclining to red. Hardness = 5.5. Sp. gr. = 6.1, —6.3.
Description.—Colour silver-white, inclining to copper-red. Occurs regularly crystallized; in granular distinct concretions, massive, disseminated,
Mineralogy. and reticulated. Lustre shining, glistening, and metallic. Fracture conchoidal. Brittle. Easily frangible.
Geognostic and Geographic Situations.—Occurs in beds, in mica slate, associated with iron and copper-pyrites, magnetic iron-ore, anthophyllite, tourmaline, felspar, &c. in parish of Modum, in Norway, also at Tunaberg, in Sweden. In some transition districts it is found in veins along with various ores of iron and copper.
2. Octahedral Cobalt-Pyrites, or Tin-White Cobalt.—Jameson.
Octaedrischer Cobalt-kies, Mohs.—Weisser Speisskobald, Werner.—Cobalt Arsenical, Haüy.
Specific Character.—Tessular. Cleavage hexahedral, octahedral, dodecahedral, but very indistinct; sometimes the hexahedral is more distinct. Tin-white, inclining to steel-grey. Hardness =5.5. Sp. gr. =6.0, =6.6.
Description.—Colour tin-white, inclining to steel-grey. Occurs regularly crystallized; in lamellar and granular concretions; massive, disseminated, reticulated, fruticose, specular. Lustre shining, splendid, and metallic. Fracture uneven. Brittle, and easily frangible.
Geognostic and Geographic Situations.—Occurs in veins in primitive and transition rocks; also in old red sandstone, and in copper-slate. Cornwall, Hesse, Thuringia, Hartz, &c. afford many localities of this mineral.
* Grey Cobalt Pyrites.—Jameson.
Grauer Speisskobalt, Werner.—Cobalt Arsenical Amorphe, Haüy.
On the fresh fracture is steel-grey, but on exposure becomes greyish-black. Occurs massive, tubiform, and specular. Lustre glistening, glistening, and metallic, but the specular variety is splendid. Fracture uneven, conchoidal, or even. Brittle. Shining in streak. Same hardness as hexahedral cobalt-pyrites. Brittle. Sp. gr. =7.0. Occurs in veins in primitive rocks in Cornwall.
** Cobalt-Kies.—Haussmann.
Colour pale steel-grey, which on exposure becomes nearly copper-red. Occurs massive, disseminated, and in cubes. Lustre shining and metallic. Fracture uneven or conchoidal. Semihard. Occurs in a bed of copper pyrites in gneiss, at Riddarhyttan, in Sweden.
*** Radiated Tin-white Cobalt Pyrites.—Jameson.
Strahliger Weisser Speisskobald, Werner.
Colour tin-white, passing into steel-grey. Occurs massive, disseminated, and reniform; also in scopiform and stellular radiated, and fibrous concretions. Lustre glistening and metallic. Fracture uneven. Softer than octahedral cobalt pyrites. Occurs in Saxony and Norway, but is a rare mineral.
Genus IV.—IRON PYRITES.
Tessular, rhomboidal, prismatic. Yellow. Hardness =3.5, =6.5. Sp. gr. =4.4, =5.0.
1. Hexahedral Iron-Pyrites.—Jameson.
Hexaedrischer Eisen-Kies, Mohs.—Gemeiner Schwefel-Kies, Werner.—Fer Sulphure, Haüy.
Specific Character.—Tessular. Combination, semitectural of parallel planes. Bronze-yellow. Hardness =6.0, =6.5. Sp. gr. =4.7, =5.0.
Description.—Colour bronze-yellow, sometimes inclining to steel-grey. Occurs regularly crystallized; in granular concretions, massive, disseminated, globular, and cellular. Lustre ranges from shining to glistening, and is metallic. Fracture uneven and conchoidal. Opaque. Brittle.
Geognostic and Geographic Situations.—The cellular varieties are rare, and hitherto have been met with principally in Saxony; while the others occur in all countries, and more or less extensively distributed through rocks of every description, from those of the oldest primitive, to the newest alluvial formations.
2. Prismatic Iron Pyrites.—Jameson.
Prismatischer Eisenkies, Mohs.—Fer Sulphure Blanc, Haüy.
Specific Character.—Prismatic. Pyramid =115° 53'; 89° 11'; 125° 16'. Cleavage, P+∞ =106° 36'. (Fig. 30.) Colour bronze-yellow. Hardness =6.0, =6.5. Sp. gr. =4.7, =5.0.
Description.—Colour bronze-yellow, inclining sometimes to steel-grey, or to brass-yellow. Occurs regularly crystallized; in radiated, granular, and lamellar concretions; massive, dendritic, reniform, globular, stalactitic, botryoidal, fruticose, and with impressions. Lustre varies from glistening to glistening, and is metallic. Opaque. Brittle. Easily frangible.
The varieties in radiated concretions are named radiated pyrites; those in which the colour inclines to brass-yellow, and which, on exposure to air, acquire a brown tarnish, are named hepatic pyrites; those in spear-shaped twin and triple crystals, spear-pyrites; and lastly, those in which the crystals are so aggregated as to have the form of the comb of the cock, are named cockscomb-pyrites.
Geognostic and Geographic Situations.—This species of iron-pyrites occurs more frequently and abundantly in newer than in older formations. The newest secondary formations, and those of the alluvial class, both in this island and on the continent of Europe, afford numerous localities of the radiated varieties. The spear-pyrites is met with in Bohemia and Saxony; and the cockscomb-pyrites in veins in Derbyshire, and in some mines in Saxony.
3. Rhomboidal Iron-Pyrites.—Jameson.
Rhomboedrischer Eisenkies, Mohs.—Magnetkies, Werner.—Fer Sulphuré Ferrifère, Haüy.
Specific Character.—Rhomboidal. Rhomboid unknown. Combination di-rhomboidal. Cleavage, R = ∞. Less distinct P+∞. Colour bronze-yellow, inclining to copper-red. Hardness =3.5, =4.5. Sp. gr. 4.4, =4.7.
Description.—Colours intermediate between bronze-yellow and copper-red. Occurs rarely crystallized; in granular concretions, also massive and dis-
Mineralogy. seminated. Lustre ranges from splendid to glistening, and is metallic. Fracture conchoidal and uneven. Opaque. Brittle. Easily frangible.
Geognostic and Geographic Situations.—This mineral occurs disseminated in primitive and transition rocks, and also disposed in beds in rocks of the same classes, in Scotland, England, Saxony, &c.
Genus V.—COPPER PYRITES.
Pyramidal. Hardness = 3.5, —4.0. Sp. gr. = 4.1, —4.3.
1. Pyramidal Copper-Pyrites, or Yellow Copper-Pyrites.—Jameson.
Pyramidal Kupfer-kies, Mohs.—Kupfer-kies, Werner.—Cuivre pyriteux, Haüy.
Specific Character.—Pyramidal. Pyramid 109° 53'; 108° 40'. Combination hemi-pyramidal, of inclined planes. Cleavage, P+1=101° 49'; 126° 11'. Brass-yellow.
Description.—Colour brass-yellow. Occurs regularly crystallized; massive, disseminated, in flakes, dendritic, reniform, botryoidal, stalactitic, and specular. Internally shining, glimmering, and metallic. Fracture uneven and conchoidal. Brittle, and easily frangible.
Geognostic and Geographic Situations.—This species of pyrites is found in all the great classes of rocks, and not only in veins, but also in beds, and in vast imbedded masses. The copper mines in England afford it in great variety and abundance; and it occurs also in Scotland, but in smaller quantities.
UNDETERMINED PYRITES.
1. Nickeliferous Grey Antimony.
Antimoine Sulphure Nickelifere, Haüy.
Tessular. Cleavage, hexahedral, perfect. Metallic lustre. Colour steel-grey, somewhat inclining to silver-white. Hardness = 5.0, —5.5. Sp. gr. = 6.4, —6.6. Occurs in veins along with galena, sparry-iron, and copper-pyrites, in the principality of Nassau.
2. Tin-Pyrites.
Etain Sulphuré, Haüy.
Colour intermediate between steel-grey and brass-yellow. Occurs massive, and disseminated. Internally glistening, shining, and metallic. Fracture uneven, inclining to conchoidal. Brittle, and easily frangible. Hardness = 4.0. Sp. gr. = 4.350, Klaproth. Occurs in copper mines in Cornwall.
Order XI.—GLANCE.
Lustre metallic. Grey, black. Hardness = 1.0, —4.0. Sp. gr. = 4.0, —7.6. If sp. gr. under 5.0, and cleavage monotonous, the colour is lead-grey. If sp. gr. above 7.4, the colour is lead-grey.
Genus I.—COPPER-GLANCE.
Tessular, prismatic. Hardness = 2.5, 4.0. Sp. gr. = 4.4, —5.8. If sp. gr. above 5.0, the colour is blackish-lead-grey. If sp. gr. under 5.0, it is steel-grey, or black.
1. Tetrahedral Copper-Glance.—Jameson.
Tetraedrischer Kupfer-glanz, Mohs.—Fahlerz, Schwarzerz, Werner.—Cuivre gris, Haüy.
Specific Character.—Tessular. Combination semi-tessular of inclined planes. Cleavage, octahedral. Colour steel-grey, ... iron-black. Hardness = 3.0, —4.0. Sp. gr. = 4.4, —4.9.
Description.—Colour steel-grey, and iron-black. Occurs regularly crystallized, massive, and disseminated. Lustre externally splendid and metallic, internally shining, or glistening, and metallic. Fracture conchoidal or uneven. Opaque, brittle, and easily frangible.
The grey varieties are named grey copper; the black, black copper.
Geognostic and Geographic Situations.—The grey varieties occur in veins in transition granite, and syenite, at Fassney Burn, in East-Lothian; at Airthrie, in Stirlingshire; in Ayrshire, and in Devonshire. The black varieties are found in transition rocks, at Claesthal, in the Hartz.
2. Prismatoidal Copper-Glance.—Jameson.
Prismatoidischer Kupfer-glanz, Mohs.—Prismatic Antimony Glance, J.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, . (Fig. 29.) Blackish lead-grey. Brittle. Hardness = 3.0. Sp. gr. = 5.7, —5.8.
Description.—Colour blackish lead-grey. Crystals in oblique four-sided prisms. Lustre shining and metallic.
3. Prismatic Copper-Glance, or Vitreous Copper.—Jameson.
Prismatischer Kupfer-glanz, Mohs.—Kupferglas, Werner.—Cuivre Sulphuré, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, (nearly). . (Fig. 30, 29.) Sectile in a high degree. Blackish lead-grey. Hardness = 2.5, —3.0. Sp. gr. = 5.5, —5.8.
Description.—Colour blackish lead-grey. Occurs regularly crystallized, also in granular concretions, and massive. Lustre glistening, glimmering, and metallic. Fracture conchoidal and uneven. Opaque. Sectile, and rather easily frangible.
Geognostic and Geographic Situations.—Occurs in veins at Fassney Burn; in the rocks of Fair Isle; in Yorkshire, Caernarvonshire, and Cornwall.
* Variegated Copper.—Jameson.
Buntkupfererz, Werner.—Cuivre Pyriteux Hepatique, Haüy.
Colour between copper-red and pinchbeck-brown, but soon obtains a variegated tarnish. Occurs in cubes truncated on the angles, and massive. Lustre shining and metallic. Cleavage octahedral. Fracture conchoidal. Sp. gr. = 5.03.
Geognostic and Geographic Situations.—Occurs in veins in primitive, transition, and secondary rocks. Found in Cornwall and other mining districts.
* Argentiferous Copper-Glance.
Silber Kupfer-glanz, Hausmann.
Mineralogy. Colour blackish lead-grey. Massive, and disseminated. Internally shining or glistening, and metallic. Fracture flat, conchoidal. Lustre increased in the streak. Soft. Sectile. Rather difficultly frangible. Sp. gr. = 6.255, Stromeyer. Occurs along with copper-pyrites, calcareous spar, and hornstone, at Schlagenberg, in Siberia.
*** Plumbiferous Copper-Glance.
Bleifahlerz, Hausmann.
Prismatic. Cleavage, P—∞. Less distinct, P+∞ = 95° (nearly). Pr+∞. Pr+∞. Metallic lustre. Steel-grey, inclining to lead-grey. Hardness = 2.5, —3.0. Sp. gr. = 5.7, —5.8. Occurs in veins that traverse clay-slate in the Hartz.
**** Tennantite.—Phillips.
Tessular. Cleavage, dodecahedral. Colour lead-grey, inclining to iron-black. Streak reddish-grey. Hardness = 4.0. Sp. gr. = 4.375, Phillips. Occurs in veins of copper-ore in Cornwall.
***** Eukairite, or Seleniferous Copper-Glance.—
Berzelius.
Colour lead-grey. Occurs massive. Lustre shining and metallic. Fracture fine grained, uneven. Opaque. Soft. Can be cut with the knife, and receives an impression from the hammer. Streak shining. Powder of streak-grey. This remarkable copper-glance, which contains twenty-six parts of the new metal named Selenium, occurs in an old copper mine in Smaland, in Sweden.
Genus II.—SILVER-GLANCE, OR VITREOUS SILVER.
Silber-glanz, Mohs.
Tessular. Blackish lead-grey. Hardness = 2.0, —2.5. Sp. gr. = 6.9, —7.2.
1. Hexahedral Silver-Glance.—Jameson.
Hexaedrischer Silber-glanz, Mohs.—Glaserz, Werner.—Argent Sulphuré, Haüy.
Specific Character.—Tessular. Cleavage not discernible. Malleable.
Description.—Colour blackish lead-grey. Occurs regularly crystallized; massive, disseminated, in plates, dentiform, filiform, capillary, reticulated, dendritic, stalactitic, and with impressions. Lustre shining, glistening, and metallic. Fracture uneven or conchoidal. Completely malleable. Flexible, but not elastic.
Geognostic and Geographic Situations.—It is one of the most common of the ores of silver. It was formerly met with at Airthrie in Stirlingshire, and is still found in the mines of Cornwall.
Genus III.—GALENA, OR LEAD-GLANCE.
Tessular. Pure lead-grey. Hardness = 2.5. Sp. gr. = 7.0, —7.6.
1. Hexahedral Galena, or Lead-Glance.—Jameson.
Hexaedrischer Bleiglanz, Mohs.—Bleiglanz, Werner.—Plomb sulphuré, Haüy.
Specific Character.—Tessular. Cleavage, hexahedral.
Description.—Colour lead-grey. Occurs regularly crystallized; in granular, prismatic, and lamellar concretions; massive, disseminated, specular, reticulated, botryoidal, and corroded. Lustre splendid to glimmering and metallic. Fracture even, or flat conchoidal. Fragments cubical. Sectile. Uncommonly easily frangible.
The variety with glimmering lustre, and even or conchoidal fracture, is named compact galena.
Geognostic and Geographic Situations.—This mineral, which is the species from which all the lead of commerce is obtained, occurs in every lead mine, whether in primitive, transition, or secondary rocks.
* Blue Lead.—Jameson.
Blau Bleierz, Werner.
Description.—Colour between dark indigo-blue and dark lead-grey. Occurs massive, and in six-sided prisms. Is glimmering and metallic. Fracture uneven, or small conchoidal. Opaque. Streak shining. Sectile, and easily frangible. Is rare, and hitherto has been found principally in lead mines in Saxony and France.
Genus IV.—TELLURIUM-GLANCE, OR BLACK TELLURIUM.
Tellur-Glanz, Mohs.
Prismatic. Cleavage, montomous. Hardness = 1.0, —1.5. Sp. gr. = 7.0, —7.2.
1. Prismatic Tellurium-Glance.—Jameson.
Prismatischer Tellur-glanz, Mohs.—Nagyagerz, Werner.—Tellure natif auro-plombifère, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, axotomous, or prismatoidal, and very perfect. Blackish lead-grey. Iron black.
Description.—Colour blackish lead-grey, and iron-black. Occurs regularly crystallized; massive, disseminated, and in leaves. Lustre splendid and metallic. Sectile.
Geognostic and Geographic Situations.—Occurs in veins that traverse porphyry, in Transylvania.
Genus V.—MOLYBDENA, OR MOLYBDENA-GLANCE.
Molybdän-Glanz, Mohs.
Rhomboidal. In thin leaves. Easily flexible. Hardness = 1.0, —1.5. Sp. gr. = 4.4, —4.6.
1. Rhomboidal Molybdena.—Jameson.
Rhombodrischer Molybdän, Mohs.—Wasserblei, Werner.—Molybdene sulphuré, Haüy.
Specific Character.—Rhomboidal. Rhomboid unknown. Combination di-rhomboidal. Cleavage R—∞, perfect. Pure lead-grey.
Description.—Colour fresh lead-grey. Occurs regularly crystallized; massive, disseminated, in plates, and in granular concretions. Lustre splendid or shining and metallic. Sectile, approaching to malleable.
Geognostic and Geographic Situations.—Occurs imbedded in granite and syenite at Peterhead; in chlorite-slate in Glenelg; in granite and syenite in Corybury, at the head of Loch Creran, and in various mines in Cornwall.
The sulphur yellow mineral which sometimes incrusts molybdena is named molybdena ochre.
Prismatic. Pure lead-grey. Hardness = 2.0, — 2.5. Sp. gr. = 6.1, — 6.4.
Prismatischer Wismuth-Glanz, Mohs.—Wismuth-Glanz, Werner.—Bismuth sulphuré, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage . . . (Fig. 30, 29, 28.)
Description.—Colour pale lead grey. Occurs regularly crystallized; in granular and radiated concretions; massive and disseminated. Internally splendid and metallic. Soils. Brittle, inclining to sectile. Easily frangible.
Geognostic and Geographic Situations.—Occurs in veins in Cornwall.
Wismuth-ocker, Werner.
The yellow, grey, or green mineral which sometimes accompanies bismuth-glance, is the bismuth ochre of mineralogists.
Antimon-Glanz, Mohs.
Prismatic. Hardness = 1.5, — 2.5. Sp. gr. = 4.0, — 5.8. If Sp. gr. under 5.0, the hardness = 2.0, and if sp. gr. above 5.0, the colour is steel-grey.
Prismatischer Antimon-glanz, Mohs.—Schrift-erz, Werner.—Tellure natif auro-argentifère, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, , perfect. Less distinct, . (Fig. 29, 28.) Pure steel-grey. Hardness = 1.5, — 2.0. Sp. gr. = 5.7, — 5.8.
Description.—Colour steel-grey. Occurs regularly crystallized; massive, disseminated, and in leaves. Externally splendid, internally glistening, and metallic. Fracture uneven. Rather brittle.
Geognostic and Geographic Situations.—Occurs in porphyry veins in Transylvania.
Grau Spiesglaserz, Werner.—Prismatoidischer Antimon-Glanz, Mohs.—Antimone sulphuré, Haüy.
Specific Character.—Prismatic. Pyramid ; ; . Cleavage, , perfect. Less distinct, . . . (Fig. 29, 27, 30, 28.) Lead-grey. Hardness = 2.0. Sp. gr. = 4.0, — 4.6.
Description.—Colour lead-grey. Occurs regularly crystallized, in radiated, fibrous, and granular distinct concretions. Lustre ranges from glistening to splendid, and is metallic. Fracture even and uneven. Rather brittle, and easily frangible.
Geognostic and Geographic Situations.—Occurs in
veins that traverse greywacke, at Westerhall, in Mineralogy. Dumfries-shire, and in Banffshire in primitive rocks.
Axentheilender Antimon-Glanz, Mohs.—Triple Sulphuré d'Antimone, Plomb et Cuivre; Endellione, Bourbon.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, , very perfect. (Fig. 27.) Steel-grey. Hardness = 2.0, — 2.5. Sp. gr. = 5.5, — 5.8.
Description.—Colour steel-grey. Occurs regularly crystallized, and massive. Lustre externally shining, internally glistening, and metallic. Fracture uneven or conchoidal. Opaque. Very brittle, and easily frangible.
Geognostic and Geographic Situations.—Occurs in veins in clay-slate in Cornwall.
Prismatic. Black, partly inclining to lead-grey. Hardness = 2.0, — 3.0. Sp. gr. = 5.9, — 6.6.
Diprismatischer Melan-Glanz, Mohs.—Schwarz Spiesglaserz, Werner.—Plomb Sulphuré-Antimonifère, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, . , the latter somewhat more discernible, but both imperfect. (Fig. 28, 29.) Iron-black, inclining to lead-grey. Hardness = 2.5, — 3.0. Sp. gr. = 6.4, — 6.6.
Description.—Colour iron-black, inclining more or less to steel-grey. Occurs regularly crystallized, and massive. Lustre shining, splendid, and metallic. Fracture conchoidal. Rather brittle, and easily frangible.
Geognostic and Geographic Situations.—Occurs in veins in primitive and transition rocks, in Transylvania and Saxony.
Prismatischer Melan-Glanz, Mohs.—Sprödglaserz, Werner.—Argent Antimone-Sulphuré Noire, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, (nearly). , imperfect. (Fig. 30, 29.) Iron-black. Hardness = 2.0, — 2.5. Sp. gr. = 5.9, — 6.4.
Description.—Colour between iron-black and dark lead-grey. Occurs regularly crystallized and disseminated. Lustre externally splendid, internally shining, and metallic. Fracture conchoidal and uneven.
Geognostic and Geographic Situations.—Occurs in veins in primitive rocks in Hungary.
Hardness = 1.0, — 4.0. Sp. gr. = 3.9, — 8.2. If the lustre is metallic, the colour is black. If the lustre is not metallic, it is adamantine. If the streak is brown, white, or grey, the sp. gr. is between 4.0,
Mineralogy. and 4.2, and the form tessular. If the streak is red, the sp. gr. = 4.5, and more; and the hardness = 2.5, and less. If the sp. gr. = 4.3, and more, the streak is red.
Genus I.—MANGANESE-BLENDE.
Glanz-Blende. Mohs.—Mangan-Blende, Werner. Prismatic. Streak green. Hardness = 3.5, —4.0. Sp. gr. = 3.9, —4.0.
1. Prismatic Manganete-Blende.—Jameson.
Prismatisches Glanz-Blende, Mohs.—Manganese Sulphuré, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage prismatic. Metallic aspect.
Description.—Colour iron-black, which, on exposure, becomes brownish-black. Occurs regularly crystallized, in granular concretions, massive, and disseminated. Lustre splendid, shining, and metallic, inclining to imperfect metallic. Opaque. Streak greenish-grey.
Geognostic and Geographic Situations.—Occurs in Cornwall and in Transylvania in primitive and transition rocks.
Genus II.—ZINC-BLENDE, or GARNET-BLENDE.
Granat-Blende, Mohs.
Tessular. Streak grey, white, reddish brown. Hardness = 3.5, —4.0. Sp. gr. = 4.0, —4.2.
1. Dodecahedral Zinc-Blende.—Jameson.
Dodecaedrische Granat-Blende, Mohs.—Blende, Werner.—Zinc Sulphuré, Haüy.
Specific Character.—Tessular. Combination, semi-tessular of inclined planes. Cleavage dodecahedral.
Description.—Colours brown, yellow, grey, green, red, and black. Occurs regularly crystallized, also in granular and fibrous distinct concretions, massive, and disseminated. Lustre ranges from specular splendid to glimmering, and is adamantine. Ranges from transparent to opaque. Brittle, and easily frangible.
The varieties in which the yellow colours predominate are named yellow zinc-blende; those in which the brown colour predominate brown zinc-blende; and, lastly, those in which black is the characteristic colour are named black zinc-blende.
Geognostic and Geographic Situations.—Beautiful yellow varieties are met with in the old lead mines of Tyndrum in Perthshire; the brown, or common blende, in every lead mine in England and Scotland; while the black variety, which is the rarest, occurs in small quantity in Saxony, and some other mining countries on the Continent of Europe.
Genus III.—ANTIMONY-BLENDE, or RED ANTIMONY.
Purpur-Blende, Mohs.
Prismatic. Hardness = 1.0, —1.5. Sp. gr. = 4.5, —4.6.
1. Prismatic Antimony-Blende, or Red Antimony.
Prismatische Purpur-Blende, Mohs.—Roth Spiesglas-erz, Werner.—Antimoine Oxidé Sulphuré, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage prismatoidal. Streak cherry-red. Mineralogy.
Description.—Colour cherry-red, and frequently with a tempered-steel tarnish. Occurs regularly crystallized; in granular, and scopiform, and stellular fibrous concretions. Lustre shining and adamantine. Opaque, or translucent on the edges.
Geognostic and Geographic Situations.—Occurs in small quantity in primitive rocks, in Saxony, France, and Hungary.
Genus IV.—RUBY-BLENDE.
Rubin-Blende, Mohs.
Rhomboidal. Hardness = 2.0, —2.5. Sp. gr. = 5.2, —8.2.
1. Rhomboidal Ruby-Blende, or Red Silver.—Jameson.
Romboedrische Rubin-Blende, Mohs.—Rothgiltigerz, Werner.—Argent Antimoine Sulphuré, Haüy.
Specific Character.—Rhomboidal. Rhomboid = 109° 28'. Combination sometimes with different planes on opposite extremities. Cleavage, rhomboidal. Streak cochineal-red. Hardness = 2.5. Sp. gr. = 5.2, —5.8.
Description.—Colour between cochineal-red and dark lead-grey, and sometimes inclines to carmine-red. Occurs regularly crystallized; massive and disseminated. Lustre ranges from splendid to glimmering, and is adamantine. Fracture uneven or conchoidal. Ranges from opaque to transparent.
Geognostic and Geographic Situations.—In some silver mines it is an abundant ore, and in this country has been hitherto found only in Cornwall.
2. Peritomous Ruby-Blende, or Cinnabar.—Jameson.
Rubin-Blende, Mohs.—Mercure Sulphuré, Haüy.
Specific Character.—Rhomboidal. Rhomboid = 71° 48'. Cleavage, R + ∞, perfect. Streak scarlet-red. Hardness = 2.0, —2.5. Sp. gr. = 6.7, —8.2.
Description.—Colours cochineal and scarlet-red, and sometimes inclines to dark steel-grey. Occurs regularly crystallized; in granular and globular concretions; massive, disseminated, and dendritic. Lustre ranges from splendid to glimmering, and is adamantine, verging on semi-metallic. Fracture uneven, conchoidal, and earthy. Ranges from transparent to opaque. Sectile, and easily frangible.
The dark coloured varieties, inclining to steel-grey, are named hepatic cinnabar, the others common cinnabar.
Geognostic and Geographic Situations.—Common cinnabar and hepatic cinnabar are the minerals that afford all the mercury of commerce. The first occurs in beds, and imbedded in porphyry rocks and those of the coal formation, while the other appears to be entirely confined to those of the coal formation. The mercury mines of Idria, Almadin, and of Deux-Ponts, afford all the known varieties of this important metalliferous mineral.
Order XIII.—SULPHUR.
No metallic lustre. Colour yellow, red or brown. Prismatic. Hardness = 1.0, —2.5. Sp. gr. = 1.9,
Mineralogy. 3.6. If sp. gr. above 2.1, the streak is yellow or red.
Genus I.—SULPHUR.
Prismatic. Hardness = 1.5, —2.5. Sp. gr. = 1.9, —3.6.
1. Prismatoidal Sulphur, or Yellow Orpiment.—Jameson.
Prismatoidischer Schwefel, Mohs.—Gelb-Rausch gelb, Werner.—Arsenic Sulphuré, Haüy.
Specific Character.—Prismatic. Pyramid unknown. Cleavage, distinctly prismatoidal. Streak lemon-yellow. Hardness = 1.5, —2.0. Sp. gr. = 3.4, —3.6.
Description.—Colour lemon-yellow. Occurs regularly crystallized; in granular and concentric lamellar concretions; massive, disseminated, stalactitic, reniform, botryoidal, and in crusts. Lustre splendid, between adamantine and semi-metallic. Translucent. Sectile. Flexible, but not elastic.
Geognostic and Geographic Situations.—Occurs in veins in various metalliferous formations in primitive and secondary rocks in Hungary and Germany.
2. Hemi-prismatic Sulphur, or Red Orpiment.—Jameson.
Hemiprismatischer Schwefel, Mohs.—Roth-Rausch gelb, Werner.—Arsenic Sulphuré Rouge, Haüy.
Specific Character.—Prismatic. Pyramid = 138° 15'; 121° 35'; 74° 21'. Combination hemi-prismatic.
. Cleavage, . Less distinct, . . (Inclination of to .) (Fig. 36, 30, 28.)
Streak orange-yellow . . . morning-red. Hardness = 1.5, —2.0. Sp. gr. = 3.3, —3.4.
Description.—Colour aurora-red, inclining sometimes to orange-yellow. Occurs regularly crystallized; massive, disseminated, and in flakes. Lustre shining, and adamantine. Fracture uneven. Translucent and semi-transparent. Brittle, and easily frangible.
Geognostic and Geographic Situations.—Generally occurs in veins in primitive rocks, and sometimes also in those of secondary formations in Germany and other countries.
3. Prismatic Sulphur, or Common Sulphur.—Jameson.
Prismatischer Schwefel, Mohs.—Natürlicher Schwefel, Werner.—Soufre, Haüy.
Specific Character.—Prismatic. Pyramid = 107° 19'; 84° 24'; 143° 8'. Cleavage, . (Fig. 30.) Streak white or sulphur-yellow. Hardness = 1.5, —2.5. Sp. gr. = 1.9, —2.1.
Description.—Colours yellow, brown, and grey. Occurs regularly crystallized; in granular distinct concretions; massive, disseminated, stalactitic, vesicular, and corroded. Lustre ranges from shining to glimmering, and is between adamantine and resinous. Fracture uneven, splintery, or conchoidal.
Translucent and transparent. Brittle, and easily frangible. Mineralogy.
Geognostic and Geographic Situations.—This mineral occurs in considerable quantities, along with gypsum, in secondary rocks in Spain and other countries; also in alluvial formations in the vicinity of sulphureous springs, and is very abundantly formed in some active volcanoes in Italy and Iceland.
CLASS III.
Specific gravity under 1.8. If liquid, the smell is bituminous. If solid, is tasteless.
Order I.—RESIN.
Hardness = 0, —2.5. Sp. gr. = 0.7, —1.6. If sp. gr. = 1.2, and more, the streak is white or grey.
Genus I.—MELLITE, or HONEY-STONE.
Melichron-Resin, Mohs.
Pyramidal. Hardness = 2.0, —2.5. Sp. gr. = 1.4, —1.6.
1. Pyramidal Mellite, or Honey-Stone.—Jameson.
Pyramidales Melichron-Resin, Mohs.—Honigstein, Werner.—Mellite, Haüy.
Specific Character.—Pyramidal. Pyramid = 118° 4', —93° 22'. Cleavage pyramidal, but imperfect.
Description.—Colours yellow or red. Occurs regularly crystallized and massive. Lustre shining or splendid, and vitreo-resinous. Fracture conchoidal, semi-transparent, or translucent. Brittle.
Geognostic and Geographic Situations.—This rare and remarkable mineral has hitherto been found only associated with brown coal at Artern in Thuringia.
Genus II.—MINERAL-RESIN.
Erd-harz, Mohs.
Amorphous. Hardness = 0.0, —2.5. Sp. gr. = 0.8, —1.2.
1. Yellow Mineral-Resin or Amber.—Jameson.
Gelbes Erd-harz, Mohs.—Bernstein, Werner.—Succin, Haüy.
Specific Character.—Solid. Yellow...white. Streak white or grey. Hardness = 2.0, —2.5. Sp. gr. = 1.0, —1.1.
Description.—Colours yellow and white. Occurs massive and disseminated, and often incloses insects, leaves, and other parts of vegetables, also corals, &c. Lustre ranges from splendid to glistening, and is resinous. Fracture conchoidal. Transparent and translucent. Brittle, and easily frangible.
Geognostic and Geographic Situations.—This beautiful mineral occurs in greatest abundance and variety imbedded in the various strata of the alluvial class, and the finest masses are those found in the low, flat, and alluvial countries on the shores of the Baltic. It has been sometimes gathered on the coasts of Scotland and England.
2. Black Mineral-Resin.—Jameson.
Schwarzes Erd-harz, Mohs.—Bitume, Haüy.
Specific Character.—Solid...liquid. Black, brown, red, and grey. Streak black, brown, yellow, and grey. Hardness = 0.0, —2.0. Sp. gr. = 0.8, —1.2.
Description.—Colours white, grey, yellow, brown,
Mineralogy. and black. Occurs massive, disseminated, globular, reniform, stalagmitic, and liquid. Lustre resinous, and ranging from splendid to glimmering. Fracture earthy, conchoidal, and slaty. Ranges from transparent to opaque.
The yellowish-white, yellowish-grey, and wine-yellow, liquid transparent varieties are named naphtha; the blackish-brown, liquid, and translucent or opaque varieties are named mineral ore, or petroleum; the blackish-brown solid varieties, with earthy fracture, are described under the name Earthy Mineral-pitch; the pitch-black varieties, with splendid and shining lustre and conchoidal fracture, are the slaggy mineral-pitch, or asphaltum of authors; and lastly, the brown, massive, curved slaty, and elastic varieties are named elastic mineral-pitch.
Geognostic and Geographic Situations.—The naphtha and mineral-oil flow from rocks of limestone and of the coal formations. The finest varieties of the former are found on the shores of the Caspian, the latter occurs at St Catharine's, in the vicinity of Edinburgh, and in several other places in Scotland and England. The earthy mineral pitch is a rare mineral, and has been hitherto found principally in the Hartz; the slaggy mineral-pitch is met with imbedded in the limestone, ironstone, and sandstone of the coal formation in the middle district of Scotland; and the elastic mineral-pitch has been hitherto found only in the lead mine called Odin, to the north of Castletown in Derbyshire.
Order II.—COAL.
Streak brown and black. Hardness =1.0, —2.5. Sp. gr. =1.2, —1.5.
Genus I.—MINERAL COAL.
Amorphous. Hardness =1.0, —2.5. Sp. gr. =1.2, —1.5.
1. Bituminous Mineral-Coal.—Jameson.
Harzige Stein-kohle, Mohs.
Specific Character.—Colours black and brown. Resinous lustre. Bituminous smell. Hardness =1.0, —2.5. Sp. gr. =1.2, —1.5.
Description.—Colours brown, black, and grey. Occurs massive, ligniform, and rarely in columnnated concretions. Lustre ranges from splendid to glimmering, and is resinous. Fracture earthy, conchoidal, slaty, and uneven. Opaque. Streak shining. Sectile or brittle. Easily frangible.
Those varieties of bituminous coal, in which brown is the predominating colour, with feeble lustre, more or less of the woody texture or form, and easily frangible, are named brown coal, under which division is included the fibrous, earthy, aluminous, conchoidal, and trapezoidal brown-coal of authors. The varieties in which the black colour predominates, and the resinous lustre, is considerable, and which are harder than the brown varieties, are named black-coal, of which the following kinds are enumerated by mineralogists, viz. slate-coal, cannel-coal, foliated-coal, and coarse-coal.
Geognostic and Geographic Situations.—The brown coal occurs principally along with rocks of the alluvial class, and the coal of Bovey in England may serve as an example of it in this island; the black-
coal never occurs in alluvial formations, always in beds in secondary rocks, and principally in that group or series of strata and beds named the coal formation. The principal coal-mines in Scotland and England are situated in the coal formation.
2. Glance-Coal.—Jameson.
Harzlose Steinkohle, Mohs.—Anthracite, Haüy.—Glanzkohle, Werner.
Specific Character.—Colour black. Imperfect metallic lustre. No bituminous smell. Hardness =2.0, —2.5. Sp. gr. =1.8, —1.5.
Description.—Colour generally iron-black. Occurs in fibrous and columnar distinct concretions; massive, vesicular, and disseminated. Lustre ranges from splendid to glimmering, and is imperfect metallic or silky. Fracture conchoidal, uneven, and slaty. Opaque. Some varieties soil. The varieties with splendid lustre and conchoidal fracture are named conchoidal glance-coal; those with slaty structure slaty glance-coal; the columnar varieties columnar glance-coal; and the fibrous and soiling varieties fibrous glance-coal or mineral charcoal.
Geognostic and Geographic Situations.—Glance-coal, like black-coal, occurs in beds in the coal formation in the secondary class of rocks within the middle division of Scotland, and Kilmarnock, Salt-coats, and Sanquhar, may be mentioned as localities; it also occurs in veins and imbedded masses in secondary trap, as in the Calton-Hill at Edinburgh. It differs from the other kinds of coal, by its occasional appearance in rocks of the primitive formation.
New Minerals.
No descriptions are here given of the minerals enumerated in the following list, because, although the accounts of them given by mineralogists are in general correct, they are not complete, and it would have extended this article much beyond the limits prescribed to it, to have detailed all that has been published in regard to them.
- 1. Allophane.
- 2. Bismuthic silver.
- 3. Blædite.
- 4. Brewsterite.
- 5. Fluor of Cerium.
- 6. Comptonite.
- 7. Conite.
- 8. Cronstedite.
- 9. Couzeranite.
- 10. Giesekite.
- 11. Gismondite.
- 12. Heulandite.
- 13. Hisengerite.
- 14. Humite.
- 15. Ligurite.
- 16. Melite.
- 17. Molybdenic silver.
- 18. Orthite.
- 19. Polyhallite.
- 20. Pyralloite.
- 21. Pyrothite.
- 22. Pyrosillite.
- 23. Sapparite.
- 24. Skorodite.
- 25. Spinnellane.
- 26. Stilpnosiderite.
- 27. Sordawallite.
- 28. Thomsonite.
- 29. Wavellite.
- 30. Yttrocerite.
- 31. Zurlite.
Plates.
The figures in the Plates of Mineralogy, from fig. Plates 27 to fig. 46, refer to the cleavage of minerals.
GEOLOGY.
GEOLOGY, as already mentioned, is that branch of History of mineralogy which treats of the atmosphere, the waters of the globe, and of the mountain rocks, of which the earth is composed. The natural history of the atmosphere is given in the article METEOROLOGY, and that of the waters of the globe under various heads of the Encyclopædia, as OCEAN, SPRINGS,
- 1. Top left: A complex crystal structure with multiple faces and internal lines.
- 2. Top middle: A vertical, elongated crystal structure with a central axis.
- 3. Top right: A vertical, elongated crystal structure with a central axis.
- 4. Middle left: A horizontal, elongated crystal structure with a central axis.
- 5. Middle center: A diamond-shaped crystal structure with internal lines.
- 6. Middle right: A small, diamond-shaped crystal structure.
- 7. Lower middle left: A vertical, elongated crystal structure with a central axis.
- 8. Lower middle center: A diamond-shaped crystal structure with internal lines.
- 9. Lower middle right: A vertical, elongated crystal structure with a central axis.
- 10. Bottom left: A vertical, elongated crystal structure with a central axis.
Geognosy. LAKES, RIVERS, &c.; and therefore our present business is with the natural history of the solid materials, of which the crust of the earth is composed. This particular department of geology is now generally known under the title Geognosy; and may be defined as that branch of mineralogy which makes us acquainted with the physiognomy of the earth's surface, and also with the internal structure, relative position, and mode of formation of the mineral masses of which it is composed.
Geognosy had scarcely an existence before the time of Saussure and Werner. The former of these celebrated philosophers, as Cuvier remarks, "by a laborious investigation of the most inaccessible mountain districts during twenty years of continual research, in which he examined the Alps on all sides, and penetrated through all their defiles, has laid open to our view the entire order of the primitive formations, and has clearly traced the boundaries by which they are distinguishable from the secondary formations. The other equally celebrated geologist, taking advantage of the numerous excavations in the most ancient mining district in the world, has fixed the laws which regulate this succession of strata, pointing out their relative antiquity in regard to each other, and tracing each of them through all its changes and metamorphoses. From him alone we date the commencement of real geognosy, so far as respects the mineral natures of the strata." Cuvier ranks next to the illustrious naturalists just mentioned. His numerous discoveries in the natural history of fossil organic remains; his inquiries into their distributions in the various mineral formations, and his elegant general views, have added much to the natural history of the globe, and contributed in an eminent degree to the advancement of geognosy. Hutton, our distinguished countryman, by the boldness and originality of his speculative views; Whitehurst, by his accurate and interesting descriptions; Playfair, by the publication of his splendid illustrations of the Huttonian theory; Greenough, Buckland, Macculloch, Jameson, and many others, by their investigation of the interesting mountains and plains of Great Britain; and the united efforts of the Wernerian Society of Edinburgh, and of the Geological Societies of London, Cornwall, and Cambridge, have, in a wonderfully short period of time, not only very greatly extended the boundaries of this science, but procured for it a host of active and intelligent cultivators; so that, at present, it is, of all the branches of natural history, that which is the most enthusiastically pursued in this island.
The principal details and theories connected with geognosy having been already given in a previous article, we shall at present confine ourselves to a short description of the physiognomy of the earth's surface; of the changes it has experienced through the agency of the atmosphere, and water; and conclude with a general account of the rocks of which the earth is composed.
Geognosy. I.—Physiognomy of the earth's surface, or description of the various inequalities observable on the dry land, and on the bottom of the sea.
On a very general view, the surface of our globe appears arranged into land and water. The water occupies nearly three-fourths of its surface, and the dry land (above its level) is arranged into masses of various forms and magnitudes. This dry land is not equally distributed; for a much larger portion of it occurs to the north than to the south of the equator; and the difference in this respect is so great, that the southern half is principally water, while the northern is chiefly land.
This great accumulation of land in the northern half of the globe suggested to some geographers the idea of the existence of a southern continent, which was necessary to counterbalance the mass of land situated in the northern hemisphere. The discoveries of Cook, however, have shown, that, up to the 70° south latitude, there is no appearance of continent; and that these dreary regions of water and ice are only diversified by a few islands. Beyond this limit, towards the pole, there remains only about five or six hundred thousand square marine leagues, in which there can be any land, inaccessible to navigators, on account of the ice, but the whole of this mass would slightly alter the proportion between the two hemispheres.* But the part of the land above the surface of the sea is so small, in proportion to the whole mass of the globe, that the effect of its unequal distribution upon the equilibrium of the globe is so inconsiderable, as to produce no sensible effect.
The dry land is arranged into two grand divisions, named Worlds, viz. the Old World, and the New World. The Old World, in the eastern hemisphere, extends from south-west to north-east, and comprehends the three continents, viz. Africa, Asia, and Europe. The New World, in the western hemisphere, extends from north to south, and is composed of two continents, viz. North and South America.
The old and new worlds have the following feature in common—northern and southern halves, connecting isthmuses, a peninsula on the one side, and a group of islands on the other. This arrangement will appear evident from the following details:
The old world may be considered as composed of two great halves, whose greatest direction is from north to south; the one, the western, includes Europe and Africa; the other, the eastern, Asia and New Holland. In the western half, the two parts or continents, viz. Europe and Africa, are connected together by the Isthmus of Suez, and have, on the one hand, the Islands of the Mediterranean, and on the other the Peninsula of Arabia. In the eastern half the two continents of Asia and New Holland are, to a certain extent, connected together by the Islands of Java, Sumatra, &c.; and in front of this broken isthmus is Papua and other islands, and on the opposite side the Peninsula of India. The new
* The lately discovered islands to the south of Cape Horn, named New South Shetland, were at first considered as portions of a Terra Australis.
Geognosy. world is composed of two halves, a northern and southern; these are connected together by the Isthmus of Darien, and on the front are situated the West India Islands, and behind the Peninsula of California.
Another general feature in the distribution of the dry land is the tending of all the great peninsulas towards the south. This is the case with Africa, Arabia, India, South America, Scandinavia, Spain, Italy, Greece, Corea, Alashka, Kamschatka, California, Florida, and Greenland.
Besides the old and new worlds, in the sense above described, there occur, dispersed through the ocean, numerous smaller masses of land, forming islands of various magnitudes and forms. Those islands, situated near to the continents, are considered as belonging to them. Thus, the British Isles belong to Europe, those of Japan to Asia, the West India Islands to America, and Madagascar to Africa. But there are other islands situated at a distance from continents, and which cannot be referred to any of the preceding divisions, but to the oceans in which they are situated.
Such are the general distributions of the land above the level of the sea; that below the waters of the ocean, or the submarine land, presents considerable variety in form and in distribution, as we shall explain particularly afterwards.
Inequalities of the Surface of the Dry Land.
The surface of the dry land exhibits great variety in aspect, forming mountains, hills, valleys, and plains. The most general divisions of these inequalities, established by geographers, are into high land and low land; and the more particular into mountain groups, hilly land, mountain chains, mountains, plains, and valleys.
HIGH LAND AND LOW LAND.
The surface of the dry land, on a general view, may be considered as composed of high land and low land. By the first we understand a lofty, uneven, and widely extended mass of land; by the second, a great and widely extended low and flat country. These high and low lands occur in all the great continents already enumerated. Thus, in Europe there is one extensive low land, bounded by two or three great high lands, which lie to the north and to the south. The southern high land has its central part in the Alps, to the east of Switzerland; towards the west it extends to the Atlantic Ocean, towards the east to the Black Sea. The northern high land comprehends the great range of Britain, that of Sweden and Norway, and some ranges in European Russia, which connect the lofty land of Norway with the Uralian range. It is between these high lands that we find the great European low land, which comprehends the northern part of France, the Netherlands, Holland, Lower Germany, Silesia, Poland, and the greater part of European Russia, to the foot of the Urals.
HIGH LAND.
These high lands are composed of chains of mountains, variously arranged in regard to each other,
and to a central and high chain; and the numerous concavities and hollows between these chains and mountains form the different kinds of valleys. Interposed between these and the low land are ranges of lower hills, forming what is called hilly land. In order to obtain a clear notion of the structure of the high land, it will be advantageous to premise a short account of the forms of single mountains, and of chains of mountains.
1. Single Mountains.
In single mountains, or hills, we can, in general, distinguish three different parts, named the foot, acclivity, and summit.
Foot.—The foot is the lowest and flattest part. It sometimes extends to a considerable distance, and then rises under an angle of or ; when it is less extensive, or has a smaller base, it rises under a somewhat greater angle, but never greatly exceeds . The mountains in wide valleys have generally a considerable foot, but in those in narrow valleys the foot is less in extent. Sometimes, as in mountains having a mural ascent, there is no foot. The inconsiderable inclination of the foot of mountains is owing to the extensive cover of debris, or alluvial soil, spread over them.
Acclivity or Ascent is the space between the foot and summit of a mountain. It is generally the steepest and most considerable part of it. Its inclination is less or more than , and on this depends the greater or less depth of the soil. Upon an acclivity of , and even more, we find a good cover of soil; at , however, the acclivity is too great to admit the growth of trees. Sometimes the acclivity is perpendicular, forming mural precipices; and it is either mural on one, two, or all sides, or in single spots. Granite, porphyry, and sandstone, afford examples of such acclivities. Humboldt remarks, in regard to acclivities in general, that they are to be reckoned considerable when their angle is or , which is the maximum for carriages; that they are very steep when , which is the maximum for loaded beasts of burthen; that an inclination of is so great, that we cannot ascend it without cutting steps in the rocks; and that, even with the aid of steps, an inclination of more than is very difficult of ascent.
Summit is generally the smallest part of a mountain, and is less steep than the acclivity. There occur, however, exceptions to this: thus, there are summits that rise more rapidly than the acclivity; and these are usually very high, almost of equal height with the acclivity, and completely bare. Summits of this description are frequent in Switzerland, where they are named peaks. In Switzerland, many of the summits are very narrow, high, and sharp, and are named needles. When the peaked or sharp conical form becomes more obtuse, obtuse conical summits are formed. When the cones become very flat and roundish they resemble domes, and such summits are said to be dome-shaped. Many summits have a convex or obtuse ridge-form, and these are named round-backed, and not unfrequently the summit is flat and like a table, when it is said to be table-shaped. These various forms of the summit
Geognosy. depend, in some measure, on the nature of the rocks; thus, soft and easily decomposable rocks present a soft outline, while those composed of hard and difficultly decomposable rocks have a very uneven and sharp contour. The position of the strata also materially affects the forms of summits, for it frequently happens, that vertically disposed hard strata form peaks and needle summits, while horizontal strata form tabular summits. The vertical strata of gneiss in some districts in Scotland, afford fine examples of the peaked and denticulated summits, some of the softer granites of Aberdeenshire of the obtuse conical summits, the clay-slate of the outer ranges of certain Highland districts of the round-backed summits, and the hills of the secondary trap formation, and of some sandstones, the table-shaped summit.
II.—Chains of Mountains.
When a greater or lesser number of hills or mountains are connected together in a lengthened form, and in a single series, they are said to form a chain of mountains. It seldom happens that single chains of mountains occur in a country, they being generally more or less numerous, and variously aggregated together.
III.—General Description of a Mountain Group, or Alpine Group.
In the higher and more central parts of the high land, many chains of mountains occur together, and in a determinate order, and form what may be denominated a mountain group, or alpine group, or system or mass of mountains. When a mountain group is viewed as a whole, it appears highest in the middle, and this highest part extends through the whole group, without being in any part of its course intersected. This elevated part we denominate the high mountain chain; it is the faite of French geologists; the juga montium, serre and sierra, of geographers.
The transverse section of a mountain group has, in general, a triangular form, in which the height bears a small proportion to the base. The two sides of the triangle form what are termed the acclivities of the group; their intersection at the upper edge, the high mountain ridge; the inferior part of each inclined plane, the foot or bottom of the group; the two small faces (the ends of the prism), the extremities of the group; its length is the distance from one extremity to the other; its breadth is that across from one foot to the other; and the height, the vertical elevation from the high mountain ridge to the level of the sea; and lastly, the point of the compass, towards which the high mountain ridge is directed, is the direction. On each of the acclivities there are chains of mountains which shoot from each side of the high mountain chain, in the manner of the ribs from the vertebral column of an animal. Between these chains, which become lower as they approach the foot of the group, are situated those great hollows or concavities named principal valleys. Some chains take their rise at the high mountain ridge, and terminate in the principal valley, before they reach the foot of the accli-
Geognosy. vity; others rise in the middle of a principal valley, and terminate at the foot of the group; and this arrangement gives rise to short valleys, having the same direction as the principal valleys, and contained in them. The acclivities of two opposite chains, which form the sides of the same valley, meet together, in a more or less tortuous line, in the bottom of the valley, or in what is termed by continental geographers the thalweg. The principal valleys, at their upper extremity or at the point of their origin, terminate in a roundish hollow which cuts the high mountain chain, and which is termed a gorge or pass. Between any two adjoining gorges, the high mountain ridge retains its primitive height, and forms a protuberance or summit; so that a high mountain chain, in its line of direction, appears denticulated or composed of an alternating series of gorges and summits. The gorges or passes are the points of departure of any two valleys on opposite sides of the group; and the summits are the points of departure of any two opposite chains. The principal mountain chains just described are again connected with others which proceed from them in a perpendicular direction; these form what are termed secondary chains, and the hollows or valleys between them secondary valleys; from these secondary chains others proceed, and give rise to tertiary chains, and tertiary valleys. Many valleys of a fourth, and even of a less considerable magnitude, occur, which do not require any further description.
IV.—Particular Description of a Mountain Group, or Alpine Group.
a. Water-Shed.
The summit of the high mountain chain is, as already mentioned, named the high mountain ridge. It is the water-shed for the whole group, and is the line formed by the meeting of the two acclivities. French geologists term it ligne de partage des eau; German geologists named it wasser scheid; and by geographers it is named divortia aquarum. The exact determination of this line is often of great importance; for example, when it is to be taken as the boundary of two neighbouring states, as was the case in the treaty of the Pyrenees (art. 42), where it was stipulated that the water-shed was to serve as the boundary between France and Spain. We must not, however, believe that the water-shed is always the highest part of a mountain group; for, as we shall afterwards explain, some of the subordinate ranges are occasionally considerably higher.
On crossing the high mountain ridge, we often pass immediately from the one acclivity of the group to the other; but in other cases, the high mountain summit is very broad, and when this takes place, we have a distance of several miles, or even leagues, before we cross from one acclivity to the other. Thus in the great alpine country of Norway, named the Lange Field, the summit of the high mountain chain varies in breadth from 24 to 36 miles. Mexico also presents a striking example of a summit which has a breadth and a length of many leagues. But even in these summits, or alpine platforms, or table lands, there is a water-shed; and it is this line which represents in every case, correctly considered, the
Geognosy. geometrical summit of the group. In some mountain groups, as the Grampians and the Pyrenees, the high mountain chain has the same general direction from one extremity to the other; in other cases, there is a change of direction; thus the Alps, after ranging from W. S. W. from St Gothard to beyond Mont Blanc, turn suddenly to the south, and maintain their new direction to the shores of the Mediterranean. During the different changes in the direction of the high mountain chain, it experiences considerable variation in height, becoming very low in some parts of its course.
b. Acclivities.
The inclined planes that proceed from each side of the high mountain chain are, as formerly mentioned, named the acclivities of the mountain group. The angle of inclination of the acclivities varies from to ; thus that of the northern acclivity of the Pyrenees is from to ; that of the southern acclivity of the Alps, from the line formed by the colossal summits of Mont Blanc, Mont Cerven, and Mont Rose, and of which the general height is 3500 metres, to the plains of Piedmont and Lombardy, is . But as such a general inclination is made up of many particular inclinations, on account of the irregularities of the acclivity, we must, before we reach the summit, ascend and descend acclivities much more considerable than that we have just mentioned. The two acclivities of a group have seldom the same degree of inclination; on the contrary, the one is generally shorter and steeper than the other. Thus the western acclivity of the Grampian mountain group is steeper and shorter than the eastern; the northern acclivity of the Erzgebirge is long and gentle, while the southern is rapid and short; in the Pyrenees, the northern acclivity is more extensive and steeper than the southern; and the western acclivity of the Andes is shorter and steeper than the eastern. These differences of inclination of the acclivities have long engaged the attention of observers, and they have endeavoured to discover some law to which they may be referred. Bergman, in his Physical Geography, maintains, that in chains having a north and south direction, the western acclivity is always the steepest; and that in chains ranging from east to west, the southern acclivity is the steepest. Dr Walker also maintained the same opinion, and used to refer to the phenomena in the Highlands of Scotland for illustrations of its truth. There can be no doubt of this arrangement occurring in some groups, but it is by no means a general one.
Andreossy, the celebrated engineer, remarks, "That when ranges of mountains are situated on the acclivities of a mountain group, such as the Jura, Vosges, Cévennes, situated on the grand acclivity descending from the Alps to the ocean, that the acclivities of the ranges looking toward the upper part of the acclivity of the group are the most abrupt;" he names it contre-pente, in opposition to the other acclivity, which being inclined in the direction of the general acclivity of the chain, bears the name simply of pente or acclivity. The observations of Saussure accord with this statement, for he says, "The inte-
rior chains turn their back to the exterior parts of the Alps, and present their escarpment to the central chain." It has also been remarked, that the mountains immediately around lakes, as those around the lake of Geneva, have their escarpment, that is, their most abrupt face, toward the lake. Geognosy.
c. Lateral and Subordinate Chains.
Those chains, which are situated on the acclivities of the group, present nearly the same phenomena as the high mountain chain. The ridges of these chains, on a general view, diminish in height as they approach their termination; but this is not always the case, because we sometimes find them maintaining their original height for a great length, and sometimes terminating abruptly. These lateral ranges also sometimes rise to a greater height than the high mountain range; thus the highest summits in the Pyrenees are not in the high mountain chain, but at a distance from it: Mont Perdu, the highest summit in the Pyrenees, is not in the high mountain chain, but in one of the lateral chains. These lateral chains have others rising from them under various angles, and thus forming another series of valleys, and these again, in their turn, in a similar way, give rise to still smaller chains and valleys.
d. Mountain Arm.
Sometimes a lateral branch or chain passes on from the foot of the acclivity into the bounding low country, and then forms what is called a mountain arm; and which, if continued to the sea, and terminates abruptly, forms a cape or promontory. In other cases, on the contrary, one of the lateral chains does not reach the foot of the mountain group, but terminates at a greater or less distance from it, and thus leaves an empty space between the extremities of two lateral chains, which are to the right and to the left of it. If the sea washes the foot of the mountain group, it invades the space between the two chains, and forms a gulf.
e. Valleys.
The concavities or hollows in a mountain group are denominated valleys. These are of various magnitudes. The principal or largest valleys are those that rise towards the high mountain chain, and which descend from it in a direction nearly perpendicular to its direction, and terminate at the foot of the group. Their general position is across the acclivity; hence they are sometimes named transverse valleys. They receive from their right and from their left, and nearly perpendicular to their direction, the valleys of the second order; and these latter valleys receive, in their turn, the valleys of the third order, or the branches of the third order, and so on of the other branches and valleys of smaller dimensions.
f. Bottom of Valleys.
As we ascend in valleys towards the chains from which they take their rise, we find that the inclination of the bottom is not every where uniform. The inclination is usually uniform and gentle, until we reach the ramifications at its upper part, when it
Geognosy. increases considerably, and sometimes we cannot reach the mountain chain but by a very steep ascent, sometimes, indeed, nearly vertical, so that the valley seems to terminate suddenly opposite to a perpendicular face. Examples of these appearances on the small scale occur in Glen Cloy, in the Island of Arran, and in Glen Corse, near Edinburgh. Beyond these precipices, in some valleys, in following the course of the water, the valley contracts and again enlarges, and this several times before reaching its termination. Most of the larger valleys present, in their course, a series of contractions and enlargements, thus forming a series of basins ranged in stages, the one above the other, and seldom communicating but by narrow openings. The valleys in the course of the Don, in Aberdeenshire, Beaully, in Inverness-shire, Tay, in Perthshire, and Nith, in Dumfries-shire, are of this description. Sausure describes several basins as occurring in the valley of the Rhone; the large and beautiful valley of Aosta, according to Daubuisson, has three basins; and the valley of the Nile, in Upper and Middle Egypt, presents a series of similar basins.
g. Salient and re-entrant Angles of Valleys.
Another curious phenomenon exhibited by valleys is their salient and re-entrant angles. "We see, in the Pyrenees," says Raymond, "some valleys whose salient and re-entrant angles so perfectly correspond, that if the force which separated them were to act in a contrary direction, and bring their sides together again, they would unite so exactly, that even the fissure could not be perceived." This appearance was first particularly noticed in the Alps by Bourguet.
h. General Direction of the great Valleys of a Group.
The direction of the principal valleys of a group, as we have already explained, is nearly perpendicular to the high mountain chain; and it is in consequence of this that valleys of this description, on a general view, and independent of local deviations, are ranged in the line of dip of the greatest acclivity. The Grampians in Scotland, and the Pyrenees in Spain, afford illustrations of this fact. But at the extremities of a high mountain chain, when the ridge becomes low, and does not rise again, the valleys ought to diverge round the point where the sinking begins; they are no longer perpendicular to the high mountain chain, and may become parallel to it. Examples of this arrangement occur in Scotland. Andreossy, speaking of such an appearance, says, "that when valleys are disposed in this manner, the mountain group to which they belong may be considered as terminated."
k. Gorges or Passes.
These are the small valleys or hollows in the high mountain chain. As these are the lowest points on the summit line of a high mountain chain, they will form the lines of communication between two countries separated by a mountain group. Notwithstanding their low situations, in regard to the neighbouring heights, they are nevertheless highly elevated above the level of the sea. The great passes lead-
ing from France into Italy afford striking examples of these short valleys; one of these, the great St Bernard, is 2500 metres above the sea; the little St Bernard, another pass, is 2200 metres above the sea; and a third, Mount Cenis, is 2060 metres above the level of the sea.
l. Forms of Mountain Groups.
The general aspect of a mountain group depends very much on the shape of the summits of the mountains of which its various chains are composed. Each group is in some degree characterized by these: In this view mountain groups are divided into common, conical, and alpine. In the common mountain group, the individual mountains of which the chains are composed are joined nearly by the summits. In the conical mountain group, the individual mountains of which the chains are composed are also singly aggregated, but not joined higher up than the acclivity; so that they appear conical. In the alpine mountain group, the mountain chains are composed, not of single mountains joined together, but of groups of pyramidal-shaped mountains, in which groups a large pyramidal mountain has arranged around it a number of smaller mountains of the same figure.
m. Connections of Mountain Groups.
Mountain groups seldom occur isolated, as is the case with the Grampians and the Pyrenees; more generally several occur together, and when this is the case, we observe that they are connected together or separated from each other in various ways. Sometimes they are separated from each other by seas; it is thus that the extremity of the Alps of Europe, or Mount Hæmus, is separated from the Caucasus by the Black Sea. In other cases they are separated by plains, placed between the foot or the extremities of the groups, as is the case with the Alps of the Tyrol, which are separated from the Böhmerwald and other mountains of Bohemia, by the plains of Bavaria. Principal valleys sometimes form the limits between two mountain groups; thus the Cevennes group is separated from the French Alps by the valley of the Rhone. Small groups of hills occasionally form the boundaries: it is thus that the Vosges are separated from the Jura group, and the Pyrenees from the Cevennes. Lastly, mountain groups are separated by natural sections; in this way the Jura group is separated from the French Alps by the deep and narrow ravine near the Fort of Ecluse.
n. Series of Mountain Groups.
Mountain groups, in regard to their connection, are either isolated, or several are joined together, forming a chain of mountain groups. A chain of mountain groups extends from the Alps of Switzerland to Servia and Bulgaria; a similar range is formed by the Fichtelgebirge, which is connected with the Carpathians by the mountain groups of the Erzgebirge, Riesengebirge, Silesian, and Moravian groups.
o. Direction of Mountain Groups.
The direction of mountain groups, and of chains
Geognosy. of mountain groups, is the same as that of the greatest dimension of the continent or island in which they occur. Thus, in Scotland, the high land, extending from Dumbarton to Cape Wrath, is in the direction of its greatest dimensions, which is from N. to S.; in the mainland of Shetland, the principal group is also in the direction of its greatest length; and in Norway, the great high land ranges from north to south, in the direction of its greatest length.
p. Basins and Lakes in Mountain Groups.
Numerous basins or concavities among mountains are filled with water, forming lakes, while others are without water, or empty. These lakes are met with principally at the foot of mountain groups, or near to their high mountain chain,—that is, at the upper extremity of the principal valleys, very near the gorges or passes. There are lakes at the highest points of the three grand passes from France into Italy by Mount Cenis, the little St Bernard, and the great St Bernard; the first is half a league in length, and the latter has a contour of three or four miles. In the valleys in the interior of mountain groups many basins occur, placed in succession above each other; and the same disposition is seen in the great valleys of rivers, far from the centre of mountain masses.
V. Hilly Land
Is composed of ranges of hills, which are irregularly grouped together, and whose elevation, in general, does not exceed 1000 feet. There is no central, or high mountain chain towards which the others tend. It forms the link which connects the mountain group with the low land, and often there is a gradual lowering of the hills until they are lost in the plains.
LOW LAND.
The low land is formed principally of large and extensive plains, little elevated above the level of the sea, on which we occasionally observe gentle risings and undulations of the surface, that often extend to a considerable distance, and sometimes form the limits between neighbouring rivers.
The plains of the low land are characterized by the presence of particular hollows, or concavities, which are denominated river-valleys, or river-courtes. In these, there are to be distinguished the bed of the river, and the holm, or haugh land: Further, there are to be observed the high and low bank of the river, and the ravines, or small valleys, that traverse the high bank and terminate in the low bank. There is still another kind of hollow met with in low land; it is that formed by shallow and wide extended lakes. Numerous instances of this appearance occur in the great European low land.
Before proceeding to describe the forms of the submarine land, we shall give descriptions of coasts and caves.
Coasts.
The edge of the dry land, where it meets the waters of the ocean, has received the general name of coast. It varies in its aspect. Sometimes it is formed of steep and rugged rocks, which are either low,
or rise to considerable height; in other cases, it is composed of shelving irregular rocks; on the coast of Holland, and in other countries, it is formed of low sandy hills termed dunes; and lastly, in the tropical seas it is more or less deeply incased with corals of various descriptions, forming what are called coral-reefs.
Caves.
These are cavities of greater or less extent, which are either open to day, or are more or less completely concealed in the interior of the earth. They are divided into external and internal caves.
1. External Caves.—These are great hollows open to day, and which occur in the faces of cliffs on the sides of valleys, and in steep cliffs and precipices near the coast, or which hang over the sea. Limestone and sandstone cliffs and precipices often exhibit caves of this description, and similar caves, sometimes of great magnitude, occur in primitive and transition rocks. The great open caves on the west coast of the Island of Arran are situated in sandstone, and the same is the case with those on the coast of Fife-shire and Angus-shire; the striking cave of Smoo, in Sutherland, is in limestone, and those of the Islands of Isla and Jura are in primitive rocks.
2. Internal Caves.—These are situated either in the centre of mountains, and without any direct communication with the atmosphere, or they are situated in the interior of rocks, but communicate with the external air by means of passages of greater or less extent. Completely included caves, and sometimes of great extent, occur in limestone, gypsum, and porphyry rocks, and others communicating by means of passages with the external air in granite, trap, and limestone rocks. The grotto of Antiparos, the caves of Derbyshire, those in several of the Hebrides, as Maclean's Cave, in the Island of Egg, &c. and some caves in the south coast of Fife-shire, are of this description.
SUBMARINE LAND.
The bottom of the sea, like the surface of the dry land, exhibits considerable variety of aspect. In some seas there occur flats and plains ranging to a considerable extent, and near to the surface of the water, forming what are named shoals; in other cases, plains of great extent occur deeply seated, or far under the surface of the ocean, and are denominated deep submarine plains. These submarine plains, like the plains on the dry land, sometimes contain hollows of considerable extent, and of great depth, which have not received any particular name. Mr Stevenson's interesting map of the German Ocean, in the third volume of the Memoirs of the Wernerian Natural History Society, presents an accurate view of the submarine plains and hollows of that part of the ocean. These submarine plains are often varied by the appearance of hilly ranges corresponding with those on the dry land.
In the tropical seas, by the accumulation of corals, numerous inequalities are formed in the submarine lands. The coral surface is always very rough and sharp, and when near the surface of the water, forms coral-reefs and coral-shoals. Sometimes the
Geognosy. inequalities are so considerable, as to form ranges of submarine coral-hills, or the rough, sharp, and rugged surface extends to a vast distance in the form of coral-plains.
II. CHANGES INDUCED ON THE SURFACE OF THE EARTH BY THE DESTROYING AND FORMING EFFECTS OF WATER AND THE ATMOSPHERE.
Having now enumerated and described the various inequalities observable on the surface of the dry land and the submarine land, we shall next give an account of the changes they have undergone by the agency of the waters of the globe and the atmosphere.
Action of Water.
Water, Werner remarks, acts mechanically, when it removes part of the soil over which it passes or corrodes the channel in which it flows, or the reservoirs in which it is contained; it also acts mechanically, when, on being imbibed by rocks, it increases their weight, and thus favours their rending, slipping, and overturning; and lastly, it acts mechanically, when, by its freezing in fissures, it breaks up mountain masses and rocks.
It acts chemically when it dissolves particular mineral substances out of the rocks through which it percolates.
DESTROYING EFFECTS OF WATER.
I. Mechanical Destroying Effects of Water.
1. Rain water, when it first touches the surface of the earth, simply moistens it; on sinking deeper, it supplies springs; and if the fall is violent, as is the case in thunder-storms and water-spouts, much of the soil is carried away, and considerable tracts are in this way bared to the naked rock. The rain water, in its progress towards the lower parts of the earth, flows either into ravines, and from these into valleys and beds of rivers; or when it meets with no furrow or ravine, scoops out a bed for itself. Torrents, when they descend from the sides of mountains, and even where the declivity of their course is not very great, produce effects which nothing but direct experience could render credible. "The fragments of rock," Professor Playfair remarks, "which oppose the torrent, are rendered specifically lighter by the fluid in which they are immersed, and lose by that means, at least, a third part of their weight; they are, at the same time, impelled by a force proportional to the square of the velocity with which the water rushes against them, and proportional also to the quantity of gravel and stones which it has already put in motion. Perhaps, after taking all the circumstances into computation, in the midst of a scene perfectly quiet and undisturbed, a philosopher might remain in doubt as to the power of torrents to move the enormous bodies of rock which are seen in the bottom of the narrow valleys or deep glens of a mountainous country; but his incredulity, says an experienced traveller, will cease altogether, if he has been surprised by a storm in the midst of some alpine region; if he has seen the number and impetuosity of the cataracts which rushed down the sides of the mountains,
and beheld the ruin which accompanied them; and if, when the tempest was passed, he has viewed those meadows, which a few hours before were covered with verdure, now buried under heaps of stones, or overwhelmed by masses of liquid mud, and the sides of the mountains cut by deep ravines, where the tract of the smallest rivulet was not to be discovered."
2. Rivers.—These occasion considerable changes in their passage from the mountains to the low country, by corroding the sides of their beds, and by breaking down their banks; and this mechanical agency is much increased when they carry along with them gravel and rolled stones. It is towards the upper part of the channels of rivers that we observe with the greatest distinctness their mechanical destroying effects on the solid strata. Professor Playfair remarks, that it is not in the greatest rivers that the power to change and wear the surface of the land is most clearly seen. It is at the heads of rivers, and in the feeders of the largest streams, when they descend over the most rapid slope, and are most subject to irregular or temporary increase and diminution, that the causes which tend to preserve, and those that tend to change the form of the earth's surface, are farthest from balancing one another; and where, after every season, almost after every flood, we perceive some change produced for which no compensation can be made, and something removed which is never to be replaced. When we trace up rivers and their branches towards their source, we come at last to rivulets, that run only in time of rain, and that run dry at other seasons. The changes of the valley of the main river are but slow; the plain indeed is wasted in one place, but is repaired in another, and we do not perceive the place from whence the repairing matter has proceeded. That which the spectator sees here does not therefore immediately suggest to him what has been the state of things before the valley was formed. But it is otherwise in the valley of the rivulet; no person can examine it without seeing that the rivulet carries away matter which cannot be repaired, except by wearing away some part of the surface of the place upon which the rain that forms the stream is gathered. The remains of a former state are here visible; and we can, without any long chain of reasoning, compare what has been with what is at this present moment. It requires but little study to replace the parts removed, and to see nature at work, resolving the most hard and solid masses, by the continued influences of the sun and atmosphere. We see the beginning of that long journey by which heavy bodies travel from the summit of the land to the bottom of the sea. In the lower and flatter districts where the strata are soft and yielding, the mechanical destroying effects of the water of rivers are often on an extensive scale. It is particularly striking when rivers pass through alluvial depositions, when they show by the successive banks and terraces on their sides the great depth to which they have worked. The alluvial matter, thus removed by the river, appears in many cases to have been deposited from the waters of lakes and the rivers con-
Geognosy. nected with them. The courses of many rivers, as Professor Playfair observes, retain marks that they once constituted a series of lakes, which have been converted into dry ground, by the twofold operation of filling up the bottoms, and deepening the outlets. This happens especially when successive terraces of gravelly and flat land are found on the banks of a river. Such platforms, or haughs, as they are called in this country, are always proofs of the waste and destruction produced by the river, and of the different levels on which it has run; but they sometimes lead us farther, and make it certain that the great mass of gravel which forms the successive terraces on each side of the river was deposited in the basin of a lake. If, from the level of the highest terrace, down to the present level of the river, all is alluvial, and formed of sand and gravel, it is then evident that the space as low as the river now runs must have been once occupied by water; at the same time, it is clear, that water must have stood or flowed as high at least as the uppermost surface of the meadow. It is impossible to reconcile these two facts, which are both undeniable, but by supposing a lake, or body of stagnant water, to have here occupied a great hollow, and that this hollow, in the course of ages, has been filled up by the gravel and alluvial earth brought down by the river, which is now cutting its channel through materials of its own depositing. It is said above, that the water must have run or stood, in former times, as low as the present bottom of the river; but there is often clear evidence that it has run or stood much lower, because the alluvial land reaches far below the present level of the river. In the course of the Tay, the Esks, the Annan, Nith, Clyde, and other rivers in Scotland, the phenomena just detailed are beautifully displayed.
3. Lakes.—In those lakes having an outlet, the water exercises a destroying effect on the interposing barrier, and next on the channel by which the water flows out, cutting it deeper and deeper until the lake is emptied. Hence the numerous basins observed in mountain countries, which still present, and well preserved, the fissure or channel through which the waters that formerly filled them made their escape. The well-known pass of the Elbe, leading from Bohemia, and that of L'Ecluse, are evidently the fissures or channels through which the waters of formerly existing lakes made them escape; and the Irongate, the famous pass through which the Danube flows from the Bannat into the plains of Wallachia, is of the same description. Thessaly appears formerly to have been in the state of a lake; but, as reported, a rent having taken place on one side of it, the water escaped with tremendous violence, devastated the lower country, and covered it with debris. The Waller Lake in the Tyrol rose so much, owing to the melting of the ice of the neighbouring glaciers, that it broke through its natural barrier; its water was precipitated with so much velocity and violence into the lower country, that whole valleys and plains were desolated and covered with rolled masses, and gravel and mud. A few years ago, a lake, of considerable extent, burst
at the top of the valley of Bagne in Switzerland, devastated the whole valley, deposited in its course vast quantities of debris, and carried to considerable distances masses of granite, some of them more than 10,000 cubic feet in magnitude. Geognosy.
Many nearly inclosed valleys or basins are to be traced in the course of the rivers of this and other countries, and all of them have been formerly in the state of lakes, or are so at present. Thus the river district of the Rhine forms many basins, of considerable magnitude, of this description, in its course towards the ocean. The basin in which the Lake of Constance is situated is one of these; a second occurs in Baden, which extends from Upper Alsace to Handruck, and the vicinity of Mayence, where the Rhine forces its way through a narrow rocky passage. The river district of the Danube forms a basin in Bavaria, through which the river flows until near to Passau, when it escapes from it by a narrow pass which leads into a second basin, which comprehends the Austrian hereditary dominions. This basin extends to Presburg, when it terminates, and the Danube again forces its way through a rocky pass into Hungary: This kingdom is a great circular valley or basin, and the Danube, after traversing it, escapes by a rocky pass into the valley of the Bannat. This inclosed valley or basin is smaller than Hungary, and opens on its lower side, and affords a passage to the river through a rocky pass into the plains of Moldavia and Wallachia, which extend from thence to the Black Sea. We have a continuation of these valleys or basins, although still filled with water, in the Black Sea, the Sea of Marmora, and the Mediterranean Sea. The great lakes in North America are also a series of basins, traversed by the river St Lawrence. The Elbe, in its course from its origin in the Riesengebirge, downwards to Meissen, in Saxony, passes from one basin to another, and exhibits such phenomena, as show the great mechanical destroying effects of its waters, and that formerly these basins were in the state of lakes. The river Don, in Aberdeenshire, the Nith, in Dumfries-shire, the Beaully, in Ross-shire, afford other examples of rivers flowing through basins that appear formerly to have been filled with water.
Sometimes the waters of lakes, in place of attacking their barriers on the upper part, pierce them below, and this effect is assisted by the presence of a rent, or fissure, which affords an opportunity for the formation of an aperture. Some of the natural bridges described by authors appear to have originated in this way.
The rending of strata by earthquakes may have afforded openings to lakes, and these bursting out thus suddenly, may have given rise to devastating, and often extensive deluges.
The numerous loose blocks of mountain rocks met with in various countries, at a great distance from any fixed masses, or strata of the same description, appear to owe their present situations to great floods of water. Masses of this kind occur in Scotland, England, Wales, Ireland, Germany, in the great valley of the Po, and in the country between the Alps and the Jura range of mountains. The
Geognosy. magnitude of these masses, which are sometimes 50,000 cubit feet in content, have engaged the particular attention both of the scientific and the curious.
The most detailed accounts of these blocks are those given by Swiss observers, and to these we shall now principally confine our attention, as they are illustrative of their distribution in other countries.
Loose blocks of alpine rocks are found in the lower part of the alpine valleys, which terminate in the great principal valley that stretches between the Alps and the Jura, from the Lake of Geneva to the Lake Constance; and are also found almost everywhere in this great principal valley. They are sometimes met with 4000 feet above the level of the sea, on the side of the Jura facing the Alps, and also in considerable numbers in many of the valleys of the Jura itself. These blocks occur only on the surface, never in any solid rock, and no one ever met with them in the subjacent strata of sandstone, marl, or conglomerate of the hills and valleys interposed between the Alps and the Jura; but they are sometimes found deep in the soil, or imbedded, or surrounded with the debris formed by rivers.
The traveller is often surprised by the enormous magnitudes of these loose blocks, some of them being calculated to contain 50,000 cubic feet. The smaller masses are distinguished from those brought down by rivers by their position, that is, their occurring on heights and acclivities where no river could ever have run. They may also be confounded with blocks from decaying conglomerate, hence it is proper to be on our guard, not only to distinguish these blocks from those derived from conglomerate rocks, but also from the rolled masses belonging to river courses.
The height at which they are found does not appear to have any relation to their magnitude, for we often find very large blocks at considerable heights, and also in deep valleys; and we also meet with small masses as well in the bottoms of valleys, as high up on the mountains.
They occur sometimes in heaps or dispersed in single blocks; but these relations have no connection with their magnitude, because we often find large and small masses in the same heap, and single, large, and small blocks on mountain summits, and in the bottoms of valleys. The smaller blocks are more or less rounded, but seldom so much so as the boulders of rivers which have been exposed to long continued friction. The larger blocks are indeed angular, but not sharp-edged. But in examining this relation, we must carefully distinguish whether or not the angles or edges are original, or have been produced by subsequent natural or artificial causes. Very often masses of this description are blasted with gunpowder, either with the view of clearing the fields, or of obtaining stones for building; and these, if left on the ground, may lead into error.
These blocks vary in their nature, some being of the primitive class, while others belong to those of the transition and secondary classes. In general, they appertain to rock formations situated nearer to the central alpine chains than those of the places where they are found. Thus no rocks of the transition class occur in gneiss valleys; no alpine lime-
stone in transition valleys; and in general, no where but in the Jura do blocks of Jura limestone make their appearance. Therefore all the loose blocks of rocks between the Jura and the Alps belong to the strata of the high chains of the Alps.
But these blocks have different characters in different districts. The loose blocks which occur in the river basin of the Rhone, and the Lake of Geneva, are quite different from those which lie strewed about in the river basin of the Rhine. These again are equally different from the loose blocks of the river basin of the Aare, as those of the Aare are from the blocks of the Lake of Zurich and the valley of Limmat; and these in their turn are equally well distinguished from the great accumulations in the valley of the Reuss. It rarely happens that intermixture takes place among these different accumulations of debris, and this is a circumstance which must be attended to in our investigation.
It results from an accurate comparison of these loose blocks with those mountain rocks which occur in extensive chains in the high Alps, that the loose blocks of every known river basin agree with the rocks which form the sides of the upper parts of those high alpine valleys which are in immediate connection with these great water basins. Thus the loose blocks of the water basin of the Rhine are similar to the rocks of Bundten. We find in the Lake of Zurich, and in the Limmat valley, the rocks of the Glarner land in loose blocks. The debris in the basin of the Reuss consists of rocks of the mountains from which the Reuss takes its rise. The loose blocks of the water basin of the Aare are similar to the mountain rocks of the high Alps of Bern; and the loose blocks, found in the course of the Rhone, occur in fixed rocks in the Vallais.
It thus appears that the loose blocks are by no means irregularly dispersed over the great valley between the Alps and the Jura, but are distributed in the direction of distinct water basins. It also appears, that the loose blocks are not irregularly distributed in these different basins; on the contrary, that in some parts of the basin they are accumulated in great numbers; in other places they are rare, and in some situations none occur.
From the preceding observations, we may obtain some hints of importance in respect to the cause of this remarkable phenomenon. These loose blocks already occur in the alpine valleys, which open into the great valley, between the Alps and the Jura. They are found more abundantly in the wide parts of valleys immediately below the narrow or contracted passes, and few occur in the narrow steep and rocky parts of the valleys.
Loose blocks are found, at a greater or less height, in the smaller lateral valleys that open into the transverse alpine valleys, which terminate in the great valley between the Alps and the Jura. If these lateral valleys form passes (which lead over into other valleys by a lowering of the high mountain chain) which are not more than 4000 feet above the level of the sea, loose blocks occur, not only in these passes, but also more or less widely distributed in the opposite valleys. In the great principal valley which stretches between the Alps and the Jura, from
Geognosy. the Lake of Geneva to beyond the Lake Constance, we find these loose blocks dispersed over all the hills whose elevation is not more than 3000 feet above the level of the sea; but even here, the distribution of the blocks is not entirely irregular. The largest are found on such hills and acclivities as are opposite the mouths of the alpine valleys, in the great principal valley. The blocks are frequently found higher on such acclivities than on the sides of those valleys which may be considered as a continuation of the alpine valleys. The loose blocks are found every where on that acclivity of the Jura range which is opposite to the Alps, and they are found highest and largest in those places which are directly opposite the mouths of the alpine valleys. In such places, the blocks again attain an elevation of nearly 4000 feet above the level of the sea; whereas in the intermediate places, which are most remote from the places opposite the mouths of the alpine valleys, the blocks seldom reach at a height of 2000 feet above the level of the sea.
In those places where the Jura chain branches into the great valley between the Jura and the Alps, loose blocks are found in the valleys behind the projecting chains. The Jura range is sometimes intersected in places opposite to the Alps; and it is remarked, that loose blocks are met with in the valleys behind these intersected portions of the range; and that, when loose blocks occur in the Jura range at a distance from the Alps, it is only in such places as are directly opposite to the intersected portions of the chain opposite to the Alps.
The circumstance of the non-occurrence of these blocks in the sandstone, marl, and nagelfluh, which occupies the great valley between the Alps and the Jura, proves that that revolution of our globe by which these were dispersed, took place after the formation of these rocks, and may therefore have belonged to one of the latest changes which have contributed to the present form of the earth's surface.
When we compare the relations of the alluvium of the rivers in valleys with those of the loose blocks, their similarity must strike every one. Thus, rolled masses are seldom deposited in those places where a river forces its way through a narrow passage; but where an expansion takes place, owing to the distance of the banks increasing, the rolled masses are sometimes accumulated in whole banks. In the same manner loose blocks seldom occur in the narrow passages of the transverse valleys in the Alps; but as soon as widenings of the valleys take place below these narrowings, the blocks occur in abundance.
If, during a flood, a rupture takes place in the banks of a river, where it is contracted, a part of the stream will flow out by the lateral opening, and carry along with it rolled masses, even when the opening in the bank does not reach to the bottom of the bed of the river; for the mountain stream, loaded with boulders, carries them not merely in single masses along its bottom, but the flood water of the stream generally attacks large sand-banks, or older beds of rolled masses, and carries along with it, accompanied with a terrible noise, whole masses, forces them over the lower banks, or through the chasm in the bank, and often deposits them several feet high on
an immediately succeeding widening of the river's course. Geognosy.
In the same manner, we observe loose blocks deposited on high situations in the lateral valleys of the great transverse valleys, and dispersed over the passes into the neighbouring valleys. The height of the lateral deposits of loose blocks, and their position in the passes and their passing into neighbouring valleys, are facts which assist us in judging of the extent of the power that may have acted during their transportation.
The striking agreement observable in the phenomena of the distribution of the loose blocks from the interior alpine valleys to the interior valleys of the Jura, with those in the rolled masses carried along by rivers, must lead every one, who reflects on this interesting phenomenon, to the hypothesis, that these blocks may have been deposited in their present situations by an immense flood which burst from the Alps. It is true, that this opinion is liable to many objections; but still it contains a more plausible explanation of the phenomenon than any other with which we are acquainted.
The loose blocks in the different river districts being in general separated from each other, or if any intermixture takes place of the rolled masses of one valley with that of another, it being only on their edges, it is highly probable that the floods which burst from these valleys, and carried along with them the masses of rocks, may have been simultaneous, by which the flood of the one basin would bound and limit that of the other, and thus prevent the water flood of one basin flowing into the neighbouring ones.
The contemporaneous occurrence of these different floods from the alpine valleys, can alone in this hypothesis explain why this aqueous flood was so generally and so highly accumulated in the great valley between the Alps and the Jura, as to reach the height of most of the sandstone mountains, and to a great elevation on the Jura, where many blocks are found deposited. But if the contemporaneous occurrence of these floods is proved by the facts, already enumerated, to what cause are we to refer this simultaneous bursting of floods of water from so many alpine valleys?
We observe, on the north-western side of the chain of the Alps, numerous openings, which, by their structure, seem to point out the action of violent floods. Let us suppose the numerous valleys, in the districts already described, closed at their present entrances, or openings, as would seem from their structure to have been formerly the case; the consequence of this arrangement would be the filling of the alpine valleys with water to the height of the lowest passes among the mountains, and thus an enormous accumulation of water would take place. This great body of water, if let loose at once, by the bursting of the lower extremities of the valleys, would form a flood which would sweep across the sandstone mountains between the Alps and the Jura range, and even ascend high on the Jura itself. This flood of water, moving probably at the rate of 200 feet in a second, and loaded with debris of rocks, would carry masses, even those having a magnitude of 50,000 cubical feet, some thousand feet high on
Geology. the Jura range.* But to what cause are we to attribute this effect? This is a question we cannot answer.
4. Ocean.—The waters of the ocean exercise a powerful destroying effect on the borders of the basins in which they are contained. If the coasts are bold and rugged, they are violently assaulted by the waves of the ocean; the crags and cliffs split and tumble down in frightful and irregular succession, and if the sea is not too deep in proportion to the mass of land, the debris accumulates at their feet, and in a longer or shorter period of time, a bank of these fragments rises at the foot of the cliff, reaches the surface of the water, even rises above it, and thus a barrier is formed which protects the cliffs from the future assaults of the ocean. If the coasts surround an island whose bulk is inconsiderable in comparison of the depth of the surrounding sea, the whole in the course of time is broken down and buried under the waves of the ocean, and in the place of an island there is formed a rocky shoal.
The perforated rock, the Doreholm, on the west coast of Shetland; the perforated rocks described by Captain Cook, near New Zealand; the stalks, holms, and skerries, on the coasts of Shetland, Scotland, Norway, &c. are effects of the destroying power of the waves.
In those rocky coasts where the strata are of unequal hardness, the softer portions, and also part of the surrounding harder mass, are removed by the action of the waves, and thus form the caves so frequently met with on sea coasts. These caves often occur at a considerable distance from the present margin of the basin of the ocean, owing to the interposition of a greater or less extent of newly formed alluvial land. Caves also occur situated in sea cliffs at a considerable height above the level of the sea. Some of these have been formed in the following manner. The cliffs, when their bases were washed by the sea, appear to have been perforated to a considerable depth and height by the impulse of the waves; and large masses of the softer interior strata washed out, and thus internal caves have been formed, situated often several fathoms above the level of the sea. The destroying effects of the sea continuing, the cliffs concealing these internal caves yield, the
internal caves become open caves, and appear at a considerable height above the level of the sea. This mode of formation is well seen in the sandstone cliffs on the east coast of Scotland. Geology.
The waters of the ocean often occasion dreadful ravages in the low countries exposed to its fury. Holland furnishes many striking examples of its devastating power. In the year 1225, the waters of the ocean, agitated by a violent tempest, inundated the country; the Rhine, swollen, at the same time, by extraordinary rains, and retained at a great height, partly by the waters of the ocean, partly by the winds blowing in a contrary direction to its course, spread over the neighbouring country; but the tempest having suddenly subsided, the highly elevated waters retired with such velocity and force as to carry with them a considerable portion of the soil, and left in its place the sea now named the Zuyder Zee. In the year 1421, a great inundation submerged the southern part of the province of Holland, drowned 60,000 persons, and on retiring it formed, near to Dortrecht, the arm of the sea named the Bies-Boos. Florus speaks of a rising of the waters of the sea in the year of Rome 644, which forced the Teutonians, Cimbrians, and Tigurians, back from the countries they inhabited. This was occasioned by a violent north wind, which raised the water of the ocean along the coasts of the countries occupied by these nations.
Such are the general destroying effects of the water of the ocean on the margin of its basin. Let us next inquire what are the changes which it produces on the submarine land.
The motions of the sea, even during a storm, do not reach to a great depth, seldom many fathoms, and hence its destroying effects cannot, in such cases, reach far, although they are sometimes so considerable as to break rocks in pieces, and throw them upon the coasts in masses of various sizes and forms.† But the effects appear to be more considerable in the course of those great currents that traverse the ocean; such as the equinoctial current and the Gulf Stream. The great depth of water in the course of the Gulf Stream would seem to prove that the corroding influence of the water
* The velocity of the burst of water from the Glacier Lake, at the top of the valley of Bagne, and its density owing to the great intermixture of debris, is in harmony with the fact, that it moved along blocks of granite some thousand cubic feet in magnitude, and deposited some of them on the sides of the valleys at a considerable height above their bottoms.
† "In disposing of the waste of the surrounding land beyond the accumulation of the sunken banks of the German Ocean, we are not left at any loss for a disturbing cause, as this is provided by the tides and currents of the sea; and with regard to their action, we have many proofs, even at very considerable depths, by the breaking up of the wrecks of ships, the occasional drift of sea-weed, and also drift timber, into regions far distant from those in which they are spontaneously produced. The dispersion of fishes, evinced by their disappearance from the fishing grounds in stormy weather, tends to show the disturbance of the waters of the ocean to the depth of 30 or 40 fathoms. This observation I have frequently had an opportunity of making near to the entrance of the Frith of Forth. Numerous proofs of the sea being disturbed to a considerable depth have also occurred since the erection of the Bell Rock Light-house, situate upon a sunken rock in the sea, twelve miles off Arbroath in Forfarshire. Some drift-stones of large dimensions, measuring upwards of thirty cubic feet, or more than two tons weight, have, during storms, been often thrown upon the rock from the deep water. These large boulder-stones are so familiar to the light-keepers at this station, as to be by them termed travellers."—Stevenson in Memoirs of the Wernerian Nat. Hist. Society, Vol. III.
Geognosy. had been sufficient to scoop out a channel or hollow in the bottom of the sea in the line of direction of the current. When the currents of the ocean are assisted by the waves and the winds, destroying effects of great magnitude are produced. It is probably in this way that some straits have been formed. Buffon remarks on this subject, that most of those in the equatorial seas are directed from east to west, like the great equinoctial current, and that it is probable this current may have formed many of them.
5. Action of Water by its own Weight.—Water, by its own weight, contributes very much to the degradation of the surface of the globe. Sometimes large masses of rock, particularly those of a soft nature, imbibe much water, by which their weight is increased, and thus occasions breaking, and rending, and slipping of masses often of enormous magnitude. These effects, it is remarked by Bergman, take place most frequently, and to greater extent, during wet than in dry seasons. In proof of this, it may be mentioned, that in the year 1805, at the close of a wet summer, and during a very rainy day, a vast mass loosened from the Rigiberg in Switzerland. This hill, situated about 1150 metres above the valley in which it occurs, is formed of sandstone, and of a conglomerated rock named Nagelfluh, having a marly basis. On the 2d of September there loosened from it an enormous mass, 4000 metres long, 400 metres broad, and 30 metres thick; it buried in its ruins several villages, destroyed 500 persons, and raised in the bottom of the valley hills nearly 200 feet in height. In the year 1618, the once considerable town of Plurs, in Graubunden, with the neighbouring village of Schelano, were overwhelmed by a vast mass of rock, which had imbibed much water, and separated from the south side of the mountain of Corto. In the year 1714, the west side of the Diableret, in the Vallais, separated, and in its course downwards covered the neighbouring country with its ruins for two miles in length and breadth, and the immense blocks of stones and heaps of debris interrupted the course of the rivers; and lakes were thus formed. Many instances are on record of the lakes formed in this way, and of great extent, afterwards bursting, and devastating immense tracks of country.
6. Effects of the Freezing of Water.—In the temperate and colder regions of the earth the expansive power of frost in breaking up rocks is often extremely striking. In the history of Norway, and in the descriptions of northern, particularly of arctic countries, we meet with many accounts of the noises and rendings of the rocks by frost. Terrible disasters take place in alpine countries by the bursting and fall of vast masses of rock, split by the freezing of the water in their rents and fissures. Sausure, during the few days of July he passed on the Col de Geant, says, not an hour passed in which he did not hear the noise of rocks splitting and falling down the acclivities by the freezing of the water in their fissures.
7. Destroying Effects of Ice and Snow.—Water in the form of ice occasions considerable changes on the surface of the earth. Thus, when floated along in great masses by rivers, it breaks up their
banks, and thus allows them to devastate the lower Geognosy. country; and often the masses are so large, and the power of the river so great, that enormous fragments of the solid strata are thereby torn off and carried to a distance. When sea ice is forced against the cliffs and precipices of the coast, the breaking and destruction it occasions are sometimes almost incredible. For the breaking up and moving of large masses of rock, one of the most powerful engines employed by nature are the glaciers, those great accumulations of congealed water and snow which form the lower boundary of the snow line in Switzerland and other regions of the globe. These great masses, says Professor Playfair, are in perpetual motion, undetermined by the influx of heat from the earth, and impelled down the acclivities on which they rest by their own enormous weight, together with that of the innumerable fragments of rock with which they are loaded. These fragments they gradually transport to their utmost boundaries, where a formidable wall ascertains their magnitude, and attests the force of the great engine by which it was erected. The immense quantity and size of the rocks thus transported have been remarked with astonishment by every observer, and explain sufficiently how fragments of rock may be put in motion, even where there is but little declivity, and where the actual surface of the ground is considerably uneven. The fall of consolidated snow often also occasions considerable changes. In mountainous countries vast masses separate, are precipitated with great velocity, accompanied with terrible noises, carrying along with them rocks of vast size, and sometimes burying villages under them.
II.—Chemical Destroying Effects of Water.
Rain water enters the fissures of the earth in a comparatively pure state, but often issues forth again more or less impregnated with various mineral substances which it has dissolved or abraded from the strata through which it has passed. Thus, when it passes through beds of rock salt, or of rocks richly impregnated with salt, salt springs are formed, and in this way enormous quantities of salt are annually brought from the interior of the earth. The quantity of salt dissolved is sometimes so great, that internal caves or hollows are formed, whose roofs sometimes fall in, and cause great irregularities on the surface of the ground. Spring water, in passing through beds and masses of gypsum, dissolves a portion of it, and in this way sometimes occasions considerable changes in the interior of the earth. Carbonate of lime also yields to the solvent powers of water, particularly when assisted by carbonic acid. Many of the excavations in limestone hills are partly owing to this destroying effect of water. Other chemical destroying effects of a similar nature might be mentioned, but those we have just stated are the most considerable, and therefore no further detail is here necessary.
DESTROYING EFFECTS OF THE ATMOSPHERE.
The combined influence of the air and moisture of the atmosphere effects great changes on the rocks at the surface of the earth. It either simply disintegrates the rock, or not only breaks it down, but also occasions a change in its chemical constitution.
Geology. Sandstone, and other rocks of the same general description, often yield very readily to the influence of the weather; their basis or ground is washed away, and the quartz and other particles remain in the form of sand and gravel. When trap veins intersect strata, it not unfrequently happens that their outgoing or crop appears rising several feet or yards above the neighbouring strata, and crossing the country like great walls; hence, in Scotland, they are named dikes. In other cases, the outgoing of beds of rocks, as of trap, appear rising to a considerable height above the general surface. In these cases, the softer bounding strata have yielded to the gnawing influence of the weather, while the harder trap, and other rocks, more obdurate, and less liable to decomposition, has resisted longer its destroying powers. Numerous examples of these effects occur in Scotland, as in Arran, Jura, Mull, west coast of Argyle, Eigg, Rume, Skye, &c. Veins of quartz also traversing granite, gneiss, mica-slate, and clay-slate, sometimes rise above the surface, and appear as dikes.
The various mountain summits owe much of their form to the destroying influence of the atmosphere. The needles, and peaks, and pyramidal forms of Alpine regions, and the tabular and round-backed forms of lower mountains, although not entirely the effects of decomposition, as some maintain, certainly have had their original forms thereby considerably changed.
Some kinds of caves, as those in certain sandstones and limestones, owe their origin to the destroying powers of the atmosphere.
The various changes in the form of rocks, by which they assume columnar, globular, tabular, indeterminate angular forms, and fall down into scales, crusts, layers, indeterminate angular grains, and sands, are, to a certain extent, effects of the destroying powers of the atmosphere.
To the destroying influence of the atmosphere valleys owe much of their present aspect. Their sides and summits, everywhere exposed to its action, become covered with debris; and, in this way, valleys sustain much greater changes than those which are produced on their bottom by the passage of the river, and on its sides by the rushing of its torrents.
But, besides these mechanical effects, many chemical destroying changes take place through the agency of the atmosphere. Felspar is often very liable to decomposition; it breaks down, and, finally, forms a kind of porcelain clay. During its decomposition, the alkali it contains is abstracted, and carried away by the atmospheric water. Other minerals are broken down and changed, by their absorbing some of the constituent parts of the atmosphere; thus, iron-pyrites, or sulphuret of iron, an insoluble substance, is in this way converted into sulphat of iron, a soluble salt; other minerals, as those abounding in iron, have their metallic ingredient changed from an oxide into a hydrate; and iron-pyrites, when contained in coal, sometimes, by its decomposition, gives it a burnt aspect.
FORMING EFFECTS OF WATER.
Mechanical Forming Effects.
1. Rain Water.—The forming effects of rain water. VOL. V. PART II.
Geology. ter, in its course over the surface of the earth, are confined to the removal of loose earthy matters, and their deposition at the foot of the inclined planes down which it flows. When, however, the rains are violent and long continued, they carry along with them coarse gravel, and even rolled masses or boulders, of considerable magnitude. These effects taking place generally over the whole face of the earth, occasion considerable changes on its surface, by these removals and depositions of the disintegrated and broken rocky matter.
2. Springs.—Some springs deposit considerable quantities of muddy matter, and thus form flat, and sometimes even hilly tracks of country.
3. Lakes.—These give rise to great depositions of alluvial matter, and when they burst their barrier, at different times, leave on their sides series of terraces, or platforms, of which we have a fine example in the parallel roads of Glen Roy.
4. Rivers.—Rivers, in their ordinary state, when confined to their beds, do not give rise to any new formations; only it has been remarked, that, towards their mouth, they have a tendency to raise their beds. Very different is the case during floods, when they overflow their banks, and cover the neighbouring country with their waters. Then they roll along with them quantities of boulders, gravel, slime, and mud, which have been taken up from the soil over which they have passed, and these are gradually deposited over the surface of the country. The boulders are first deposited, next the gravel, and, lastly, the sand and mud. These sediments, accumulated during a long series of years, give rise to very considerable formations. The country along the banks of the Mississippi affords striking examples of the varieties and great extent of this mechanical forming effect of water. The vast plains on the sides of the Amazon River owe their formation in part to this effect of river water. Every hundred years, as we are informed by Girard, the Nile deposits on the soil of Lower Egypt a sediment of nearly five inches in thickness; and the flat lands there are composed of similar alluvial matters, and to an unknown depth. The water of rivers flowing over the same districts at different times, and not always conveying the same materials, have thus accumulated different substances above each other; and hence the alternations of beds of boulders, gravel, sand and clay, met with in countries formed by the alluvium of rivers. The soil of Egypt presents beds and veins of sand in the midst of the mud deposited by the Nile.
The beautiful holm, or haugh-lands, on the sides of our rivers, and which are often the richest parts of the country, have been formed by this mechanical agency of water. But these formations, although very considerable, are not the only ones effected by rivers. Besides the great deposits laid over the country they traverse, they carry along with them, to the shores of the ocean, and to the entrances of lakes, much disintegrated matter.
When any considerable river or stream enters a lake, a flat meadow track is formed, which continues to increase from year to year. The soil of this meadow is terminated by a marsh, which marsh is ac-
Geognosy. quiring solidity, and is soon to be converted into a meadow, as the meadow will be into an arable field. All the while the sediment of the river makes its way hourly into the lake, forming a mound or bank under the surface of the water, with a pretty rapid slope towards the lake. This mound increases by the addition of new earth, sand, and gravel, poured in over the slope; and thus the process of filling up gradually advances. These phenomena are to be seen in all the lakes that receive rivers in this and other countries. This forming effect of water is very striking in the larger lakes. Thus, where the Rhone enters the Lake of Geneva, the beach has been observed to receive an annual increase, and the Portus Valesiae, now Port Valais, which is at present half a league from the lake, was formerly close upon its banks. The great North American lakes are undergoing similar changes. In the course of ages lakes are filled up, when the country thus formed presents, in place of a lake, a plain traversed by the river. This change is effected partly by the filling up of the lake by the debris carried into it by the river, and partly by the draining off of the water by the deepening of the outlet. This latter is an operation which is generally visible. The stream, as it precipitates itself over the rocks, hurries along with it, not only sand and gravel, but also large blocks of stone, which grind and wear down the rocks, and materially assist the water in its deepening operation. Rivers, as already mentioned, carry to the sea-shore a portion of the loose matter removed from the surface of the earth by their destroying power. When they reach the sea, their velocity gradually diminishes, and is soon annihilated. As it diminishes, the coarse sand is deposited on the edges of the stream where the motion is least; and the finer particles are carried onwards to a distance from the coast. The alluvia formed in this manner at the mouths of rivers, and on their sides, by the current, are often very considerable. The Thames, Elbe, Rhine, and other rivers, afford striking examples of these formations. Prony informs us, that the River Po has so greatly raised the level of its bottom, since it was shut in by dikes, that its present surface is higher than the roofs of the houses of Ferrara. At the same time, the alluvial additions produced by that river have advanced so rapidly into the sea, that, by comparing old charts with the present state, the coast appears to have gained no less than 14,000 yards since the year 1604, giving an average of 180 to 200 feet yearly, and in some places the average amounts to 200 feet. The Nile, the Orinoco, and other great rivers in America, exhibit similar phenomena. At the mouth of the Mississippi large alluvial islands are formed, and, within the period of 100 years, the alluvial lands formed by it have extended several leagues into the sea.
The debris brought down by rivers when deposited in nearly inclosed seas, renders them shallower, and their borders are increased in extent. The Baltic has been computed to decrease in depth at the rate of forty inches in a hundred years. In proof of the increase of the shores of the Baltic, the following facts may be adduced. The Bay of Ful-
backa, which was navigated by boats within the memory of man, is now filled up, and covered with grass. Several harbours in Lapland, that formerly admitted vessels, are now 3000 or 4000 paces from the sea; and at Helsingor, there are iron-works at places which were covered by the sea about eighty years ago. The whole of the ancient kingdom of Prussia appears to have been formed by alluvial depositions; it is said that the sea reached as far as Culm within the period of credible history. Dantzic, several hundred years ago, was close to the sea-shore. The Yellow Sea, which is a large gulf contained between the coast of China and the Peninsula of Corea, and which has somewhat of the character of such seas as the Baltic, receives so much mud from the great rivers that run into it, that it takes it colour, as well as its name, from that circumstance, and computations have been made of the time that it will require to fill up this gulf, and to withdraw it entirely from the dominion of the ocean; and these, although not very satisfactory, are considered as showing that it will be filled up in 240 ages.
The alluvial matter brought down by rivers, not only forms great tracks of land at their mouths, but also by the agency of currents, assisted by the waves of the ocean, gives rise to extensive tracks of low and flat land, which extend along the coast.
It is well known that the Mediterranean is at present one league from Aigues-Mortes, in Provence, where St Louis embarked in 1269. Ravenna, which, in the time of Augustus, projected into the sea, is now nearly three miles from it; and the site of Venice and other similar situations will, in the course of time, experience the same fate. Spina had been originally built by the Greeks on the sea-coast; but in the time of Strabo, the sea was removed to the distance of ninety stadia. Adria, which gave name to the Adriatic, was, somewhat more than twenty centuries ago, the chief port of that sea, from which it is now at the distance of six leagues. The formation and increase of new grounds by alluvial depositions proceeds with equal rapidity along the coasts of the North Sea as on those of the Adriatic. These additions can easily be traced in Friesland and Groningen, where the epoch of the first dikes is well known to have been in the year 1570. An hundred years afterwards, the alluvial depositions had added in some places three-quarters of a league of new land on the outside of the dikes. The same phenomenon is distinctly observable all along the coasts of East Friesland, and the countries of Bremen and Holstein, as the period at which the new grounds were inclosed by the dikes for the first time is perfectly well known, and the extent that has been gained since it has been measured.
When the sea-coast is low, and the bottom consists of sand, the waves push this sand towards the shore, where, at every reflux of the tide, it becomes partially dried, and the winds, which often blow from the sea, drift up some portions of it upon the beach. By this forming effect of the ocean, downs, or ranges of low sand-hills, are formed along the coast. These accumulations of sand, if not fixed either by natural or artificial means, advance towards the interior of the country. In their progress inland, they push
Geognosy. before them great pools of water, formed by the rain which falls on the neighbouring grounds, and which has no means of running off, in consequence of the obstructions interposed by the downs. In several they proceed with a frightful rapidity, overwhelming forests, houses, and cultivated fields in their progress. M. Bremontier, who made extensive works with a view of stopping the progress of the downs, in the south of France, estimated their progress there at sixty feet yearly, and in some places at seventy-two feet.
Sand-banks.—These also are to be considered as forming effects of water, and the general opinion is, that they are produced sometimes by the meeting of currents, and in other cases by depositions from currents interrupted by land, whether submarine or dry land. Thus the formation of the banks on the coast of Holland, and even of the Dogger Bank itself, is ascribed to the meeting of tides, by which a state of tranquillity is produced in the waters, and of consequence a more copious deposition of their sand and mud. The great bank of Newfoundland is conjectured to be a deposition from the waters of the Gulf Stream.
Chemical Forming Effects of Water.
Springs.—Certain spring waters, after dissolving, by means of the superabundant carbonic acid with which they are impregnated, calcareous earth abraded from limestone rocks, or rocks containing calcareous matter, allow the lime to crystallize, in consequence of the escape of the acid, and in this way form depositions of calc-sinter, or calcareous alabaster, on the roofs, sides, and floors of caves, or fill up fissures in rocks, and form veins, or when flowing over the surface of rocks, incrust them with calcareous sinter, or calcareous tuffa. The water of such springs, when collected in hollows so as to form lakes, often deposits vast quantities of calcareous tuffa, and hence these lakes, when dried up, present very extensive formations of these calcareous minerals. The travertine employed for building at Rome is a calcareous deposition from the waters of springs; and the town of Guancavelica, in South America, is built of a compact calcareous tuffa from the calcareous springs in the neighbourhood. The calcareous tuffa is most generally formed in open exposed places, but calcareous sinter chiefly in inclosed spaces, such as caves, &c. The peastone of mineralogists is formed from the waters of hot springs, as those of Carlsbad in Bohemia. The hot springs of Iceland, St Michael's, &c. deposit vast quantities of siliceous sinter, and this siliceous compound, although generally pure, is not always so, being occasionally intermixed with other minerals, and thus gives rise to particular mineral substances.
Lakes.—We have already noticed the calcareous depositions from the waters of some lakes, we shall now give an account of depositions of other kinds of minerals. The bog iron-ore of mineralogists is often found in such situations as to show it had been formed by deposition from the water of lakes; and in some countries it is collected from the sides and bottoms of lakes once in a certain number of years, thus showing that it is still forming in such situations. In
salt lakes considerable depositions of salt take place, and when such collections of water dry up, or are drained off, the sides and bottom of the cavities are found incrustated with salt, which is sometimes disposed in beds alternating with layers of clay.
4. Marine Incrustations.—Collections of sea shells are sometimes found agglutinated, and form banks or beds of considerable extent. But Cuvier remarks, we have no evidence that the sea has now the power of agglutinating these shells by such a compact paste, or indurated cement, as that found in marbles, or even in the coarse limestone strata in which shells are found enveloped. Still less do we now find the sea making any depositions at all of the more solid and siliceous strata which have preceded the formation of the strata containing shells. A compact calcareous alluvial rock is found in considerable abundance on the coasts of the West India islands, by the conglutination of fragments of shells and corals. The human skeleton from Guadeloupe, in the British Museum, is imbedded in rock of this description.
GENERAL ACCOUNT OF THE DIFFERENT CLASSES OF ROCKS.
Before the time of Lehman, the formations of which the crust of the earth is composed, were believed to be destitute of all regularity in distribution and in individual characters. That intelligent miner, however, was early convinced of the existence of a certain degree of order in their arrangement, and at length, in his well known work, first stated their division into Primitive and Secondary; under the first including those destitute of fossil organic remains, and which he considered as disposed in highly inclined strata, and as forming the most lofty, rugged, and hardest parts of the surface and interior of the earth; while under the other he arranged all those containing petrifications, or fossil organic remains, or which were associated with others containing such remains, and which, he says, are disposed in strata more horizontal, and form the lower and softer portions of the surface and interior of the earth. As geognosy advanced, new facts were added to those already known, and new arrangements and distributions of the formations were discovered. Werner first pointed out another class of rocks, which he named Transition, as they exhibit such characters as show the transition from those of the primitive to those of the secondary classes. These are interposed between the primitive and secondary classes, and are the first or earliest rocks of which the crust of the earth is composed, that afford fossil organic remains. The same illustrious naturalist examined with great care the various characters of those loosely cohering rocks of clay, marl, loam, &c. which rest on the more solid and older rocks of the secondary, transition, and primitive classes, and which form a fourth class, under the title Alluvial. The various mineral masses formed by the agency of volcanoes were but slightly noticed by Lehman, but claimed much of the attention of Werner, who formed them into a fifth class, under the title of Volcanic.
These different classes of rocks are met with in most extensive tracts of country, and every where
Geology. exhibit the same general relations. Thus the primitive rocks of Scotland, on a general view, do not differ from those of New Holland, and the rocks of the secondary class, although at first sight presenting much of a local character, are the same in all parts of the world where they have been hitherto met with.
I. Primitive Rocks.
The rocks of this class lie under those of the succeeding classes, and frequently, owing to the inequalities of their original surface, rise through them, and often to a great height, in the form of mountains and mountain chains. Countries composed of primitive rocks are in general more rugged and lofty than those of the other classes; further, their cliffs are more extensive, their valleys narrower and deeper, and more uneven than those in secondary countries. The strata of primitive mountains are very frequently highly inclined, a circumstance which contributes, in an especial manner, to the increase of the ruggedness and inequalities of the surface of primitive regions. The primitive strata in many countries maintain a wonderful uniformity of direction; thus, in Scotland, the general direction of the strata of the primitive mountains is from N. E. to S. W., and the same is the case nearly in the vast alpine regions of Norway, and in many of the lofty and widely extended primitive lands of other parts in Europe. In Scotland the direction is so invariable, not only in the primitive but also in the transition strata, that travellers may use it in place of a compass in guiding themselves through the mountain wilds of our Highland regions. The rocks of which primitive mountains and plains are composed are, throughout, of a crystalline nature, and present such characters as intimate their formation from a state of solution. These characters are the intermixture of the concretions of which these are composed at their line of junction, their mutual penetration of each other, their considerable lustre, pure colours, and considerable translucency. Thus, in granite, the concretions of felspar, quartz, and mica, are joined together without any basis or ground, and at their line of junction are either simply very closely attached together, or are intermixed, and frequently branches of the one concretion shoot into the other, thus occasioning a mutual interlacement, as is observed in bodies that have been formed simultaneously, and from a state of solution. These characters show that the concretions of granite, and the same applies to the concretions in limestone, gneiss, mica-slate, and other rocks of the primitive class, are of a crystalline nature, and have been formed at the same time.
The strata themselves are so arranged in mountains, that is, one set of strata including another, as to render it probable, that the seams of the strata are not a mechanical effect, but have been produced in the same manner as the seams of distinct concretions, or the surfaces of crystals. These strata, collected in groups, give rise to formations, such as gneiss or mica-slate; and in those cases where the rock is not distinctly stratified, it exhibits such characters as point it out in an unity or formation in the grand series, of which the crust of the earth is composed. The rock formations in primitive countries, although well marked
and distinguished by their general and particular characters, are not in any case isolated or unrelated to each other; on the contrary, we find, as they approach and join each other, gradual transitions of the one into the other, or intermixtures and interlacings at their great lines of junction. No true primitive rock appears foreign to the others, or exhibiting such characters as intimate a different mode of formation. Thus granite, which some consider a kind of lava, and therefore formed in different manner from gneiss or mica-slate, passes into and is intermixed with the surrounding rocks, and therefore has been formed in the same manner.
Primitive rocks are distinguished from those of the succeeding classes, by the absence of all fossil organic remains. This important fact allows us to infer, that organic beings had not been called into existence during the formation of primitive rocks, so that there was a time, in the history of the formation of our planet, when plants and animals did not exist. Although no traces of organic life occur in primitive rocks, yet they afford beds of a kind of coal (glance coal), almost entirely composed of carbon, a substance which many consider as peculiar to the organic kingdom, and which, they maintain, when found in the mineral kingdom, is to be traced to previously existing organic beings. This opinion is disproved, not only by the facts already mentioned, but also by the occurrence of carbon in hornblende, slate, and other minerals of the primitive class. Here then we have the formation of carbon, independent of the agency of animals and vegetables.
Limestone has been by many considered as entirely the result of animal action, and the various formations of that rock, whether in primitive or secondary mountains, are viewed as accumulations of altered shells or corals. But neither shells nor corals occur in primitive mountains, although they often contain extensive beds of limestone; and further, lime enters as a constituent part into most of the simple minerals of which primitive rocks are composed, facts which show that lime, like carbon, is an original substance in primitive mountains, and therefore has been formed at times independent of animals.
The two most abundant alkalies, viz. natron and potash, occur in primitive mountains, but of these, the potash is by far the most frequent and abundant. Before the discovery of potash in lepidolite, a primitive mineral, by Klaproth, this alkali was considered as entirely a production of the vegetable kingdom; but no vegetable remains occur in primitive rocks; and, therefore, in this case, the potash has been formed by some other agency than that of vegetation.
Phosphat of lime, which forms so important a constituent part of the higher animals, was long maintained to be exclusively a production of the animal kingdom; its after discovery in some vegetables, demonstrated that it also was occasionally produced in some tribes of plants; but still it was believed to be in every case either of animal or vegetable origin. But geologists, by the discovery of apatite, or phosphat of lime, in primitive mountains, have proved its existence in nature, independent of the agency of the organic kingdom.
Primitive rocks abound very much in metalliferous
Geognosy. rous minerals, and hitherto no metal has been met with which does not occur exclusively, or occasionally, in this class of rocks. Tin, wolfram, and molybdena, occur more frequently in these rocks than in other situations. Gold, silver, lead, copper, iron, cobalt, zinc, manganese, arsenic, and mercury, occur either disseminated, in beds, veins, or imbedded, in various rocks of this class, and many primitive districts are particularly characterized by the metaliferous repositories they contain; thus, the primitive district of Strontian is characterized by its particular venigenous formation of galena, or lead-glass; the primitive country of Königsberg, in Norway, by its group of veins of silver-ore; and the primitive gneiss rocks of Arendal and Lapland, by their beds of magnetic iron-ore.
The most beautiful of all the productions of the mineral kingdom, the gems, occur in great variety in primitive rocks. Nothing can be more beautiful than the drusy cavities met with in primitive mountains, whose walls are lined with pure and variously coloured and crystallized topaz, beryl, and rock crystal; and the gneiss, granite, and mica-slate, with their imbedded grains and crystals of sapphire, crysoberyl, and garnet; and the veins in granite, clay-slate, and other primitive rocks, with their emeralds, axinite, and spinel ruby, afford to the mineralogist highly interesting combinations.
But the most precious of all the gems, the diamond, is wanting in primitive regions. Judging of it from its splendid lustre, pure and beautiful colours, high degree of translucency, and great hardness, we would have expected it to occur in the cavities or veins of primitive rocks. But it is far otherwise, for it appears only in alluvial formations of gravel, clay, and sand, of new formation, removed at an immense distance from those that form the grand basis of the crust of the globe; thus intimating its recent, and probably vegetable origin.
From what has been already said, it is evident that the study of these rocks must be highly interesting, in an economical point of view. Many of the richest and most important mines in the world are situated in primitive rocks; statuary marble, and the various granites, porphyries, and serpentines, so much valued in the arts; and the gems, so distinguished by their beauty of lustre, colour, and great hardness, are principally contained in formations of the primitive series.
Different Primitive Rocks.
The following are the rocks that occur in primitive mountains, viz. granite, porphyry, trap, serpentine, limestone, gneiss, mica-slate, clay-slate, and quartz rock.
These rocks are very simple in their nature, being generally composed of not more than five minerals, viz. quartz, felspar, mica, hornblende, and limestone. Some rocks are composed of but one of these simple minerals, as quartz rock; others of two, such as mica-slate, which is a compound of mica and quartz; and others, as granite, consist of three of them, viz. quartz, felspar, and mica. In determining the species of primitive rocks, we must have an accurate acquaintance with the five simple minerals
Geognosy. already enumerated, and with the aspects they assume when forming these aggregate mountain rocks. This being the case, nothing more is necessary than to refer the reader to the characters of these simple minerals given in the mineralogy of this article, and now to give short characters of the rocks themselves.
1. Granite is a granular compound of felspar, quartz, and mica; syenite is a variety of granite, containing, besides the ingredients already enumerated, also hornblende.
2. Porphyry is an aggregate rock, having a basis or ground containing imbedded grains and crystals of felspar, and sometimes of quartz and hornblende.
3. Trap.—All the rocks of the primitive class in which hornblende is the predominating ingredient are named trap. On exposure to the air they assume the form of steps of a stair, hence the name trap. When the hornblende is associated with felspar, it forms greenstone; if unmixed, hornblende rock; and if slaty, hornblende slate.
4. Serpentine is a dark green rock, with a splintery fracture, and glimmering or dull lustre, translucent on the edges, and so soft as to yield readily to the knife. It is conjectured to be a compound of felspar, and of a mineral of the nature of hornblende, named diallage.
5. Limestone.—This rock has generally a white or grey colour, is composed of shining granular concretions, and is more or less translucent. It frequently contains scales of mica and grains of quartz.
6. Gneiss is a granular slaty compound of felspar, quartz, and mica.
7. Mica-slate is a slaty compound of mica and quartz.
8. Clay-slate is a slaty rock, generally composed of extremely minute scales of mica. It is the roof slate so well known in the arts.
9. Quartz-rock.—This rock is almost entirely composed of quartz, either in granular concretions, or in the compact state; and grains of felspar and scales of mica are frequently contained in it.
II.—Transition Rocks.
Transition rocks succeed to the primitive, and are followed by those of the secondary class. They generally, in this country, occupy a higher level than the secondary, but a lower one than the primitive formations. Their mountains, mountain-ranges, mountain-groups, and cliffs, are more rugged than those of the secondary class, but are less rugged and softer in their outlines than the primitive rocks. Their valleys, too, are wider, and their sides less rugged and abrupt, than in those of primitive mountain-groups.
Most of the rocks are distinctly stratified, and the strata are frequently vertical, and, like those of the primitive class, exhibit the same general direction throughout great tracks of country. Thus the strata in the great high land which ranges from St Abb's Head to the Irish Sea, and which is almost entirely composed of transition rocks, range everywhere nearly from N. E. to S. W.
Although most of the transition rocks appear to have been formed from a state of solution, and there-
fore possess the crystalline character, yet their crystallization appears to have been less perfect than in the primitive rocks, because the parts of which they are composed have a lower degree of lustre, inferior hardness, less translucency, and colours of less purity, than primitive rocks. In short, on a general view, we would say, these rocks have more of the earthy aspect, and of the fragmented character, thus intimating a lower degree of crystallization, than is observable in the primitive class. But transition rocks are further distinguished from those of the primitive class, by the very important circumstance of their containing fossil organic remains. These petrifications are of corals and shells, animal productions low in the zoological scale; and of vegetable remains that appear to belong to plants of the most simple construction, such as those of the class cryptogamia, and therefore at the bottom of the botanical scale. Hence it follows, that animals and vegetables of the more simple construction were those first called into existence, and that their creation did not take place until the period of the formation of transition rocks. Corals of the same nature as those met with in the preceding class also occur in transition rocks; and numerous and extensive beds of limestone, sometimes containing organic remains, are in some districts of frequent occurrence. Transition rocks frequently abound in ores of various descriptions, which are generally disposed in veins. The mining districts of the Leadhills and Wanlockhead, near Edinburgh, which are so rich in galena, or lead-glance, are situated in transition rocks. The rich lead and silver mines in the Hartz, and many of those in Mexico, are in rocks of the same description.
The gems which appear in so many interesting forms and relations in the strata and veins of primitive mountains, are comparatively rare in the present class.
The abundant occurrence of ores in this class of rocks; the extensive deposits of limestone, particularly of the variegated kinds so highly prized for ornamental purposes, which they contain; the fine granites and porphyries which they afford, are sufficient proofs of their importance in the arts.
The following are the rocks belonging to this class, viz. greywacke, clay-slate, limestone, trap, granite, syenite, porphyry, serpentine, gneiss, mica slate, and quartz-rock.
1. Greywacke is a conglomerated looking rock, with a basis of clay-slate, including angular and various shaped portions (by many considered as fragments) of clay-slate, flinty-slate, quartz, felspar, &c. and occasionally scales of mica. When the imbedded masses become small, and the mass slaty, it is named greywacke-slate.
2. Clay-slate.—This rock is of the same general nature with primitive clay-slate, but differs from it in having less lustre, and in sometimes containing fossil plants and fossil shells.
3. Limestone.—It is more compact, and much smaller granular, and therefore has less lustre and lower translucency than the primitive limestone. It is frequently traversed by veins of calcareous spar, and often exhibits in the same bed various tints and shades of beautiful colours. Some varieties are con-
glomerated, forming the brecciated marble of artists, and others contain fossil shells and corals. Geognosy.
4. Trap.—This rock, like that of the primitive class, is principally composed of hornblende, and is sometimes associated with felspar, forming transition greenstone.
5. Granite, Syenite, and Porphyry.—These have the same composition as in the primitive class; and, independent of the characters derived from their mass, and their particular imbedded minerals and veins, are distinguished by the greywacke, with which they are associated.
6. Gneiss and Mica Slate.—These rocks occasionally occur associated with the greywacke and other members of this class.
7. Serpentine and Quartz Rock.—These very nearly resemble those of the primitive class, but are distinguished from them by their connection with greywacke, &c.
III.—Secondary Rocks.
This extensive and very interesting class of rocks rests immediately on those of the transition class; but when these are wanting, it rests on primitive rocks; and when the rocks of the two preceding classes occur in the same district with the secondary, the two former generally occupy a higher level. The hills of secondary districts are lower, rounder, with gentler acclivities, and fewer cliffs than those in transition districts; and their valleys are shallower, and their bottoms less inclined. Nearly all the secondary formations are more or less distinctly stratified, and the strata are more frequently horizontal, or slightly inclined, than in the older rocks. That regularity of direction of the strata, so prominent in the two preceding classes, has not been observed in the present.
Many of the secondary rocks, from their conglomerated structure, present a mechanical and not chemical aspect, and even the limestones of this series approach more nearly to the mechanical formation, than is observed in those of the preceding classes.
Secondary rocks are further particularly distinguished by the great variety and abundance of fossil organic remains which they contain. These extend throughout the whole secondary series, abounding in some formations as limestone, and in others as gypsum and trap, appearing rarely, and in small quantities. In the older formations, fossil remains of oviparous quadrupeds or lizards are met with, while, in the newer members of the series, remains of true quadrupeds, as of opossums, occur; and Werner, long ago, pointed out among the secondary formations the gradual rise of the animals in the zoological scale, according to the date of the formation in which their remains were found, viz. that in the oldest secondary rocks, the animal remains were of tribes lower in organization than those met with in formations in the middle of the series, and that those found in the newest members of the class were of animals much more perfect than those in the middle part of the series.
Coal, which we have already enumerated in the primitive and transition classes, occurs in great abundance in the secondary class, and, besides the glance-coal, the only kind of coal found in the formations older than the secondary class, contains also the black
Geognosy. or bituminous coal, which has much more the aspect of a vegetable formation than the glance-coal, and brown coal, a mineral of undoubted vegetable origin.
Secondary rocks are much less metalliferous than the transition and primitive, and hitherto the principal repositories of ore have been met with in the lower parts of the series, viz. in the mountain limestone, lower part of the coal formation, magnesian limestone, and in the lower part of the new red sandstone. The most abundant metals are iron, lead, and copper, and to these, as a metal of rather abundant occurrence, may be added zinc, in the form of calamine, mercury in form of cinnabar, and cobalt. It is in the secondary class of rocks that rock-salt first makes its appearance in quantity, and in the form of imbedded masses, and beds associated with gypsum and saliniferous clay.
The gems, as we have already remarked, are almost entirely confined to the primitive class, being of comparatively rare occurrence in transition rocks, and still less frequent in the rocks of this class.
From what has been already detailed, it is evident, that this class of rocks, from the variety and abundance of useful minerals it contains, must be highly interesting to those who attend to the uses of minerals. The greatest coal mines in this island, and in other countries, are situated in secondary rocks; the richest lead mines in England, the great iron mines in England and Scotland, and the salt of Cheshire, and of other countries, the vast quarries of sandstone, so important in building, and of greenstone, which furnishes the best paving stone hitherto discovered, and of limestone, so useful for various economical purposes, are situated in the formations of the secondary class.
The principal secondary rocks are sandstone, limestone, and trap, and these are arranged in various positions, and associated with other rocks.
We shall now enumerate them in the order of their relative position.
1. First Sandstone, or Old Red Sandstone Formation.—This is a reddish-brown sandstone, principally composed of particles of quartz, either without ground, or connected together by a basis or ground of iron shot-clay. It passes into greywacke, as on the coast of Galloway. It rests upon the rocks of the transition class.
2. First Secondary Limestone, or Mountain Limestone.—is a compact bluish-grey limestone, full of encrinites, corals, and shells; often contains caverns, and sometimes alternates with the sandstone, slate-clay, and other rocks of the coal formation. It lies immediately on the old red sandstone.
3. Coal Formation.—This is an alternation of grey and white sandstone, bituminous shale and slate clay, clay ironstone, limestone, and coal. The whole together form a group or set of rocks, termed the coal formation. It rests on the mountain limestone.
4. Second Secondary Limestone, or Magnesian Limestone of Geologists.—This formation, as it appears in England, is generally a granular, sandy, and glimmering limestone, which contains a considerable portion of carbonate of magnesia. It occasionally contains gypsum and rock-salt. It lies immediately over or above the coal formation.
4. Second Sandstone, or New Red Sandstone Formation.—This sandstone is principally composed of particles of quartz, set in a reddish-brown clayey basis or ground. It is looser in its nature than the old red sandstone, and its colour wants the bluish tint which occurs in the old red sandstone. It is sometimes conglomerated, particularly where near the magnesian limestone, when it contains fragments of the subjacent strata. It abounds in beds of red and blue marl and clay, and in these there are occasionally imbedded masses and beds of gypsum and rock-salt. It is here, and in the magnesian limestone formation, that the greatest masses of rock-salt are met with, and it is in these formations of the secondary series that the principal salt mines are situated. It rests immediately on the second secondary or magnesian limestone.
5. Third Secondary Limestone, or the Oolite or Shell Limestone Formation, or Jura Formation.—The lower members of this formation are blue, grey, and white slaty limestone, with blue slaty marl, and clay, in which are variously shaped masses of chert. These are known under the name Lias. Above these, still in this formation, there are alternations of beds of oolite limestone, shelly limestone, calcareous sandstone, various marls, clays, and fuller's earth. It rests upon the second or new red sandstone.
6. Third Sandstone Formation, or the Green Sand Formation.—This formation extends through a large portion of the south-eastern parts of England. Its characteristic member is a siliceous sandstone, abounding in grains of a substance resembling green earth or augite. Besides this sandstone, the formation contains beds of a coarse shelly limestone, of various clays, fuller's earth, and of iron sand. It rests upon the third limestone or oolite formation.
7. Fourth Limestone Formation, or Chalk Formation.—The lower part of this formation is composed of a grey clayey chalk, without flints, and of grey-coloured clays and marls. Immediately above is a hard chalk, with few flints, and above is the softer chalk in which flints and organic remains abound.
8. Brown Coal Formation.—In this formation, which appears to rest upon chalk, brown coal occurs in great masses, associated with clays and marls, and occasionally with glance coal. The English pudding-stone appears to rest immediately, either on the brown coal or the chalk formations.
9. Paris Formation.—Under this head we include the series of beds of clay, marl, limestone, gypsum, sand, and sandstone, that occur in the basin of Paris, and also in that of the Isle of Wight and other quarters. They lie above chalk, and higher than the brown coal, and are divided into sets; two characterized by the presence of fresh water shells, and remains of quadrupeds, are named fresh water formations; and other two, containing principally salt water shells, are named marine formations.
10. Secondary Trap Rocks.—The rocks of this division have been described by many geologists as lavas. They occur in imbedded masses, beds and veins, in many of the formations already described, and hence, in order to prevent repetition, we have brought them together under one division. They are principally composed of augite, with occasional