the most highly valued of precious stones. The finest diamonds are perfectly transparent and colourless, of a regular form, and entirely free from flaws and veins. They have been distinguished by lapidaries into oriental and occidental. But these terms are not expressive of the country from which they are brought, but merely of their qualities and value, the oriental being reckoned the finest and hardest, and the occidental of inferior value. See Chemistry and Mineralogy Index.

Cornish DIAMOND, a name given by many to the rock crystals found in the tin mines of Cornwall. These crystals are usually bright and clear, and are found most frequently in the 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 \( \frac{1}{7} \) of the diameter of the base. The perpendicular, from the base to the crown, must be \( \frac{3}{5} \) 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 shakes, and fills the stones 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 goats 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; though its hardness be not such, that it will endure being struck at pleasure with the hammer.

Foilitious DIAMONDS. Attempts have been made to produce

produce artificial diamonds, but with no great success.

DIANA.—Those 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 be pretty considerable for the habits of the actors on the stage, &c. See PASTES.

in the glafs trade, an instrument used for squaring the large plates or pieces; and, among glaziers, for cutting their glafs.

These sorts of diamonds are differently fitted up. That used for large pieces, as looking glafes, &c. is set in an iron ferril, about two inches long, and a quarter of an inch in diameter; the cavity of the ferril being filled up with lead, to keep the diamond firm: there is also a handle of box or ebony fitted to the ferril, for holding it by.

in Heraldry, a term used for expressing the black colour in the achievements of peerage.

Guillem does not approve of blazoning the coats of peers by precious stones instead of metals and colours; but the English practice allows it. Morgan says the diamond is an emblem of fortitude.