DIAMOND-MINE of Raolconda

DIAMOND-MINE of Raolconda.—In the neighbourhood of this mine the earth is sandy, and full of rocks and copse. In these rocks are found several little veins of half and sometimes a whole inch broad, out of which the miners, with a kind of hooked irons, draw the sand or earth wherein the diamonds are; breaking the rocks when the vein terminates, that the track may be found again, and continued. When a sufficient quantity of earth or sand is drawn forth, they wash it two or three times, to separate the stones therefrom.

Diamond. from. The miners work quite naked, except for a thin linen cloth before them; and besides this precaution, have likewise inspectors, to prevent their concealing of stones: which, however, maugre all this care, they frequently find means to do, by watching opportunities when they are not observed, and swallowing them down.

DIAMOND-MINE of Gani or Coulour.—In this mine are found a great number of stones from 10 to 40 carats, and even more; and it was here that famous diamond of Aureng-Zeb the Great Mogul, which before it was cut weighed 793 carats, was found. The stones of this mine are not very clear; their water is usually tinged with the quality of the soil; being black where that is marshy, red where it partakes of red, sometimes green and yellow, if the ground happen to be of those colours. Another defect of some consequence is a kind of greasiness appearing on the diamond, when cut, which takes off part of its lustre.—There are usually no less than 60,000 persons, men, women, and children, at work in this mine.

When the miners have found a place where they intend to dig, they level another somewhat bigger in the neighbourhood thereof, and inclose it with walls about two feet high, only leaving apertures from space to space, to give passage to the water. After a few superstitious ceremonies, and a kind of feast which the master of the mine makes for the workmen, to encourage them, every one goes to his business, the men digging the earth in the place first discovered, and the women and children carrying it off into the other walled round. They dig 12 or 14 feet deep, and till such time as they find water. Then they cease digging; and the water thus found serves to wash the earth two or three times, after which it is let out at an aperture reserved for that end. This earth being well washed, and well dried, they sift it in a kind of open sieve, or riddle, much as we do corn in Europe; then thrash it, and sift it afresh; and lastly, search it well with the hands to find the diamonds. They work naked as in the mine of Raolconda, and are watched after the like manner by inspectors.

DIAMOND-MINE of Soumelpour, or river Goual.—Soumelpour is a large town built all of earth, and covered with branches of cacao-trees: the river Goual runs by the foot thereof, in its passing from the high mountains towards the south to the Ganges, where it loses its name. It is from this river that all our fine diamond points, or sparks, called natural sparks, are brought. They never begin to seek for diamonds in this river till after the great rains are over, that is, after the month of December; and they usually even wait till the water is grown clear, which is not before January. The season at hand, eight or ten thousand persons, of all ages and sexes, come out of Soumelpour and the neighbouring villages. The most experienced among them search and examine the sand of the river, going up it from Soumelpour to the very mountain whence it springs. A great sign that there are diamonds in it, is the finding of those stones which the Europeans call thunder-stones. When all the sand of the river, which at that time is very low, has been well examined, they proceed to take up that wherein they judge diamonds likely to be found; which is done after the following manner: They dam the place

round with stones, earth, and fascines, and lading out the water, dig about two feet deep: the sand thus got is carried into a place walled round on the bank of the river. The rest is performed after the same manner as at Coulour, and the workmen are watched with equal strictness.

DIAMOND-MINE in the island of Borneo, or river of Succudan.—We are but little acquainted with this mine; the queen who reigns in that part of the island not allowing strangers to have any commerce in these stones: though there are very fine ones to be bought at Batavia, brought thither by stealth. They were anciently imagined to be softer than those of the other mines; but experience shows they are in no respect inferior to them.

Beside these four diamond-mines, there have been two others discovered; one of them between Coulour and Raolconda, and the other in the province of Carnatica; but they were both closed up almost as soon as discovered: that of Carnatica, because the water of the diamonds was always either black or yellow; and the other, on account of their cracking, and flying in pieces when cut and ground.

The diamond, we have already observed, is the hardest of all precious stones. It can only be cut and ground by itself and its own substance. To bring it to that perfection which augments its price so considerably, they begin by rubbing several against each other, while rough; after having first glued them to the ends of two wooden blocks, thick enough to be held in the hand. It is this powder thus rubbed off the stones, and received in a little box for the purpose, that serves to grind and polish the stones.

Diamonds are cut and polished by means of a mill, which turns a wheel of soft iron sprinkled over with diamond-dust mixed with oil of olives. The same dust, well ground, and diluted with water and vinegar, is used in the sawing of diamonds; which is performed with an iron or brass wire, as fine as a hair. Sometimes, in lieu of sawing the diamonds, they cleave them, especially if there be any large shivers therein. But the Europeans are not usually daring or expert enough to run the risk of cleaving, for fear of breaking.

The first water in diamonds means the greatest purity and perfection of their complexion, which ought to be that of the purest water. When diamonds fall short of this perfection, they are said to be of the second or third water, &c. till the stone may be properly called a coloured one: for it would be an impropriety to speak of an imperfectly coloured diamond, or one that has other defects, as a stone of a bad water only.

Mr Boyle has observed, from a person much conversant in diamonds, that some of these gems, in their rough state, were much heavier than others of the same bigness, especially if they were cloudy or foul; and Mr Boyle mentions one that weighed 8½ grains, which being carefully weighed in water, proved to an equal bulk of that liquor as 2½ to 1. So that, as far as could be judged by that experiment, a diamond weighs not thrice as much as water: and yet, in his table of specific gravities, that of a diamond is said to be to water as 3400 to 1000; that is, as 3½ to 1; and therefore, according to these two accounts, there should be some diamonds whose specific gravity differs nearly from that of others. But this is a much greater difference

Diamond. ference than can be expected in two bodies of the same species; and indeed, on an accurate trial, does not prove to be the case with diamonds. The Brasil diamonds differ a little in weight one from another, and greatly vary from the standard set by Mr Boyle for the specific gravity of this gem in general; two large diamonds from that part of the world being carefully weighed, one was found as 3518, the other as 3521, the specific gravity of water being reckoned 1000. After this, ten East India diamonds were chosen out of a large parcel, each as different from the other in shape, colour, &c. as could be found. These being weighed in the same scales and water with the former, the lightest proved as 3512, the heaviest as 3525, still supposing the water to be 1000.—Mr Ellicot, who made these experiments, has drawn out a table of their several differences, which is done with great care and accuracy; and, taking in all the common varieties in diamonds, may serve as a general rule for their mean gravity and differences.

Therefore if any thing is to be concluded as to the specific gravity of the diamond, it is, that it is to water as 3517 to 1000.

For the valuation of diamonds of all weights, Mr Jefferies lays down the following rule. He first supposes the value of a rough diamond to be settled at 2 l. per carat, at a medium; then to find the value of diamonds of greater weights, multiply the square of their weight by 2, and the product is the value required. E. G. to find the value of a rough diamond of two carats; $2\; \backslash times\; 2\; =\; 4$, the square of the weight; which, multiplied by two, gives 8 l. the true value of a rough diamond of two carats. For finding the value of manufactured diamonds, he supposes half their weight to be lost in manufacturing them; and therefore, to find their

value, we must multiply the square of double their weight by 2, which will give their true value in pounds. Thus, to find the value of a wrought diamond weighing two carats; we first find the square of double the weight, viz $4\; \backslash times\; 4\; =\; 16$; then $16\; \backslash times\; 2\; =\; 32$. So that the true value of a wrought diamond of two carats is 32 l. On these principles Mr Jefferies has constructed tables of the price of diamonds from 1 to 100 carats.

The greatest diamond ever known in the world is one belonging to the king of Portugal, which was found in Brasil. It is still uncut; and Mr Magellan informs us, that it was of a larger size; but a piece was cleaved or broken off by the ignorant countryman, who chanced to find this great gem, and tried its hardness by the stroke of a large hammer upon the anvil.

This prodigious diamond weighs 1680 carats; and although it is uncut, Mr Romé de l'Isle says, that it is valued at 224 millions sterling; which gives the estimation of 79,36 or about 80 pounds sterling for each carat: viz. for the multiplicand of the square of its whole weight. But even in case of any error of the press in this valuation, if we employ the general rule above mentioned, this great gem must be worth at least 5,644,800 pounds sterling, which are the product of 1680 by two pounds, viz. much above five millions and a half sterling.

The famous diamond which adorns the sceptre of the Empress of Russia under the eagle at the top of it weighs 779 carats, and is worth at least 4,854,728 pounds sterling, although it hardly cost 135,417 guineas. This diamond was one of the eyes of a Malabarian idol, named Scheringham. A French grenadier, who had deserted from the Indian service, contrived so well as to become one of the priests of that idol, from which he had the opportunity to steal its eye: he ran away to the English at Trichinapety, and thence to Madras. A ship-captain bought it for twenty thousand rupees: afterwards a Jew gave seventeen or eighteen thousand pounds sterling for it: at last a Greek merchant, named Gregory Suffras, offered it to sale at Amsterdam in the year 1766: and the late prince Orloff made this acquisition, as he himself told Mr Magellan in London, for his sovereign the empress of Russia. Dutens, page 19. and Bomare, page 389. of his Mineralogy, relate the above anecdote. The figure and size of this diamond may be seen in the British Museum in London: it is far from being of a regular form.

The diamond of the great Mogul is cut in Rose; weighs 279$\backslash frac\{1\}\{2\}$ carats, and it is worth 380,000 guineas. This diamond has a small flaw underneath near the bottom: and Tavernier, page 389. who examined it, valued the carat at 150 French livres. Before this diamond was cut, it weighed 793$\backslash frac\{1\}\{2\}$ carats, according to Romé de l'Isle: but Tavernier, page 339. of his second volume, says, that it weighed 900 carats before it was cut. If this is the very same diamond, its loss by being cut was very extraordinary.

Another diamond of the king of Portugal, which weighs 215 carats, is extremely fine, and is worth at least 369,800 guineas.

The diamond of the grand duke of Tuscany, now of the emperor of Germany, weighs 139$\backslash frac\{1\}\{2\}$ carats; and is worth at least 109,520 guineas. Tavernier says, that

Diamond. that this diamond has a little hue of a citron colour; and he valued it at 135 livres tournois the carat. Robert de Berquen says, that this diamond was cut into two: that the grand Turk had another of the same size: and that there were at Bisnagar two large diamonds, one of 250 and another of 140 carats. This Robert de Berquen was the grandson of Louis de Berquen, who invented the art of cutting diamonds.

The diamond of the king of France, called the Pitt or Regent, weighs 136½ carats: this gem is worth at least 208,333 guineas, although it did not cost above the half of this value.

The other diamond of the same monarch, called the Sancy, weighs 55 carats: it cost 25,000 guineas: and Mr Dutens says, that it is worth much above that price.

Brilliant Diamond, is that cut in faces both at top and bottom; and whose table, or principal face at top, is flat. To make a complete square brilliant, if the rough diamond be not found of a square figure, it must be made so; and if the work is perfectly executed, the length of the axis will be equal to the side of the square base of the pyramid.—Jewellers then form the table and collet by dividing the block, or length of the axis, into 18 parts. They take $\backslash frac\{1\}\{18\}$ from the upper part, and $\backslash frac\{1\}\{18\}$ from the lower. This gives a plane at $\backslash frac\{1\}\{18\}$ distance from the girdle for the table; and a smaller plane at $\backslash frac\{1\}\{18\}$ distance for the collet; the breadth of which will be $\backslash frac\{1\}\{2\}$ of the breadth of the table. In this flat the stone is said to be a complete square table diamond.—The brilliant is an improvement on the table-diamond, and was introduced within the last century, according to Mr Jefferies.—To render a brilliant perfect, each corner of the above described table-diamond, must be shortened by $\backslash frac\{1\}\{18\}$ of its original. The corner ribs of the upper sides must be flattened, or run towards the centre of the table $\backslash frac\{1\}\{2\}$ less than the sides; the lower part, which terminates in the girdle, must be $\backslash frac\{1\}\{2\}$ of one side of the girdle; and each corner rib of the under sides must be flattened at the top, to answer the above flattening at the girdle, and at bottom must be $\backslash frac\{1\}\{2\}$ of each side of the collet.

The parts of the small work which completes the brilliant, or the star and skil facets, are of a triangular figure. Both of these partake equally of the depth of the upper sides from the table to the girdle; and meet in the middle of each side of the table and girdle, as also at the corners. Thus they produce regular lozenges on the four upper sides and corners of the stone. The triangular facets, on the under sides, joining to the girdle, must be half as deep again as the above facets, to answer to the collet part.—The stone here described is said to be a full-substantiated brilliant.—If the stone is thicker than in the proportion here mentioned, it is said to be an over-weighted brilliant.—If the thickness is less than in this proportion, it is called a spread-brilliant.—The beauty of brilliants is diminished from their being either over-weighted or spread. The true proportion of the axis, or depth of the stone to its side, is as 2 to 3.—Brilliants are distinguished into square, round, oval, and drops, from the figure of their respective girdles.

Cornish Diamond, a name given by many people to the crystals found in digging the mines of tin in Corn-

wal. These crystals are of the nature of the Kerry-stone of Ireland, but somewhat inferior to it: they are usually bright and clear, except towards the root, where they are coarse and foul, or whitish. They are usually found in the common form of an hexangular column terminated at each end by an hexangular pyramid.

Rose-Diamond is one that is quite flat underneath, with its upper part cut in divers little faces, usually triangles, the uppermost of which terminate in a point.—In rose diamonds, the depth of the stone from the base to the point must be half the breadth of the diameter of the base of the stone. The diameter of the crown must be $\backslash frac\{1\}\{2\}$ of the diameter of the base. The perpendicular, from the base to the crown, must be $\backslash frac\{1\}\{2\}$ of the diameter of the stone. The lozenges which appear in all circular rose-diamonds, will be equally divided by the ribs that form the crown; and the upper angles or facets will terminate in the extreme point of the stone, and the lower in the base or girdle.

Rough Diamond, is the stone as nature produces it in the mines.

A rough diamond must be chosen uniform, of a good shape, transparent, not quite white, and free of flaws and shivers. Black, rugged, dirty, flawey, veiny stones, and all such as are not fit for cutting, they use to pound in a steel mortar made for that purpose; and when pulverized, they serve to saw, cut, and polish the rest. Shivers are occasioned in diamonds by this. That the miners, to get them more easily out of the vein, which winds between two rocks, break the rocks with huge iron levers, which flakes, and fills the stone with cracks and shivers. The ancients had two mistaken notions with regard to the diamond: the first, that it became soft, by steeping it in hot goat's blood; and the second, that it is malleable, and bears the hammer. Experience shows us the contrary; there being nothing capable of mollifying the hardness of this stone; tho' its hardness be not such, that it will endure being struck at pleasure with the hammer.

Fashioned Diamonds. Attempts have been made to produce artificial diamonds, but with no great success.—These made in France, called temple diamonds, on account of the temple at Paris, where the best of them are made, fall vastly short of the genuine ones; accordingly they are but little valued, though the consumption thereof is pretty considerable for the habits of the actors on the stage, &c. See PASTES.