MARBLE, in natural history, a genus of fossils; being bright and beautiful stones composed of small separate concretions, moderately hard, not giving fire with steel, fermenting with and soluble in acid menstrua, and calcining in a slight fire.—The word comes from the French marbre, and that from the Latin marmor, of the Greek μαρμωρ, to "shine or glitter."
The colours by which marbles are distinguished are almost innumerable; but the most remarkable are, 1. The black marble of Flanders. 2. Plain yellow. 3. Yellow with some white veins. 4. Yellow with black dendrites. 5. Yellow with brown figures resembling ruins. 6. Black and yellow. 7. Black and white. 8. Pale yellow, with spots of a blackish-grey colour. 9. Yellow, white, and red. 10. Pale yellow. 11. Olive colour, with deeper coloured cross lines, and dendrites. 12. Brownish red. 13. Flesh-coloured and yellow. 14. Common red marble. 15. Crimson, white, and grey. 16. Reddish-brown lumps, on a whitish ground. 17. Bluish grey. 18. Snowy-white.
The varieties of marble, numerous as they are, have
been improperly augmented by virtuosos, and some people who collect specimens for the sake of gain. The Italians are particularly curious in this way; and most of the names imposed upon marbles are given by them. Every marble brought from an unknown place is called by them antico; when distinguished by a number of bright colours, it is called brocatello, or brocatellato. When they want some of the originals to complete a whole set of marbles, they either substitute others which have the nearest resemblance to them; or, lastly, they stain white marbles according to their own fancy, and impose them on the world as natural. The finest solid modern marbles are those of Italy, Blankenburg, France, and Flanders. It has also been lately discovered, that very fine marble is contained in some of the Western Islands of Scotland. Those of Germany, Norway, and Sweden, are of an inferior kind, being mixed with a kind of fealy limestone; and even several of those above mentioned are partly mixed with this substance, though in an inferior degree. Cronstedt, however, mentions a new quarry of white marble in Sweden, which, from the specimens he had seen, promised to be excellent.
The specific gravity of marble is from 2700 to 2800; that of Carreria, a very fine Italian marble, is 2717.—Black marble owes its colour to a slight mixture of iron. Mr Bayen found some which contained 5 per cent. of the metal; notwithstanding which, the lime prepared from it was white, but in time it acquired an ochry or reddish-yellow colour.
Marble, when chemically examined, appears to consist of calcareous earth united with much fixed air; and is, like limestone or chalk, capable of being converted into a strong quicklime.—Dr Black derives the origin of marbles, as well as limestone and marble, from the same source, viz. from the calcareous matter of shells and lithophytes. In one kind of limestone known by the name of Portland-stone, and consisting of round grains united together, it was supposed to be composed of the spawn of fish; but comparisons of other phenomena have explained it. It is plain that it has been produced from a calcareous sand, which is found on the shore of some of the islands in the southern climates. By the constant agitation the softer parts are worn off, and the harder parts remain in the form of particles that are highly polished, and which are afterwards gradually made to concrete together by causes of which we have yet no knowledge.—There are indeed some few of the limestones and marbles in which we cannot discover any of the relics of the shells; but there are many signs of their having been in a dissolved or liquid state; so we cannot expect to see the remains of the form of the shells: but even in many of the marbles that have the greatest appearance of a complete mixture, we still find often the confused remains of the shells of which they have been originally composed. We should still find it difficult to conceive how such masses should have derived their origin from shells; but, considering the many collections that we have an opportunity of seeing in their steps towards this process, and a little concreted together, so that by their going a step farther they might form limestone and marbles, we shall soon see the possibility of their being all produced in the same manner. Thus vast quantities
titles of shells have been found in the province of Turen in France; and indeed there is no place where they have not been found. The lithophyta likewise seem to be a very fruitful source of this kind of earth. In the cold climates, where the moderate degree of heat is not so productive of animal-life, we have not such an opportunity of observing this: but in the hot climates, the sea, as well as the land, swarms with innumerable animals; and, at the bottom, with those that produce the corals and madriporos. We learn from the history of a ship that was sunk in a storm in the Gulf of Mexico, the vast growth there is of these bodies. About 30 years after, they attempted to dive into it to get out a quantity of silver; but they found great difficulty in getting it, from the ship being overgrown with coral. Sir Hans Sloan, in the Philosophical Transactions, and in his history of Jamaica, observes, that the ship's timber, the iron, and money, were all concreted by the growth of the calcareous matter. So in a tract of many thousands of years the quantity of it should be very great; and as this is going on through a very great extent of the bottom of the sea, it will produce very extensive as well as massy collections of calcareous matter.
According to Sir William Hamilton †, many variegated marbles and precious stones are the produce of volcanoes.