DIAMOND-MINE

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 shews, 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

Diamond. cleave them, especially if there be any large flivers therein. But the Europeans are not usually daring or expert enough to run the risk of cleaving, for fear of breaking.

The finest diamonds are those of a complexion like that of a drop of pure water. It is likewise a valuable property if they are of a regular form and truly made; as also, that they be free from stains, spots, specks, flaws, and cross veins. If diamonds are tinctured yellow, blue, green, or red, in a high degree, they are next in esteem; but if they are tinctured with these colours only in a low degree, the value of them is greatly diminished. There are also diamonds of other complexions; such as brown, and those of a dark hue: the first resembling the brown sugar-candy, and the latter dusky iron. In the Philosophical Commerce of Arts, Dr Lewis tells us of a black diamond that he himself had seen. At a distance, it looked uniformly black; but, on closer examination, appeared in some parts transparent, and in others charged with foulness, on which the black hue depended.

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 ¼ from that of others. But this is a much greater difference 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 Elliott, 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 21. 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.

Diamonds are commonly found but of very small sizes. The largest ever seen was brought from Brasil, and is in the possession of the king of Portugal. It weighs 12½ ounces, and has been valued at upwards of 50 millions sterling. By some skilful lapidaries, however, this stone is only reckoned to be a topaz; in which case, its value must be prodigiously diminished. The largest oriental diamond in the world belongs to the great Mogul. It weighs 279 carats. According to the computation of M. Tavernier, this diamond is worth 779,244 l. Ster. but by the tables of Mr Jefferies above-mentioned,

Diamond. mentioned, its value is only 624,962 l.