DIAMOND (corrupted from Gr. adamant, untamable, refractory), the most valuable of precious stones after the ruby, and the hardest of all known substances. It consists of carbon (q.v.), a simple or elementary substance, crystallized, and in its greatest purity. Diamonds are commonly colorless and clear like water ; although sometimes, from some slight foreign intermixture, they are white, gray, yellow, green, brown, and more rarely orange, red, blue, or black. The luster is adamantine and very high; the transparency perfect in specimens perfectly free from foreign substances, the presence of which, how ever, even in very small quantity, mars it, and sometimes almost produces opacity. The D. becomes positively electric by friction, but is not electrified by heat, a test which sometimes serves to distinguish it from the topaz. Its specific gravity is about 3.6. Its primary form is a regular octahedron, but it appears also in rhombic dodecahedrons; and its crystals often have curvilinear faces and edges. Its structure is distinctly lamellar. It burns before the blow-pipe in air or in oxygen gas, combining with oxygen to form carbonic acid. Its hardness renders it incapable of being scratched by any other sub stance, and in cutting and polishing diamonds, diamond-dust is employed. The estima tion in which it is held as a precious stone is due to its remarkable hardness, rarity, and brilliancy. The art of cutting diamonds, although long practiced in India and China, was not known in Europe till after the middle of the 15th c., when it was discovered by Louis van Berguen of Bruges. Previous to that time, diamonds were set without being cut, and in that state they have often a rough, dull, and uneven surface. Diamonds arc indeed found not only in the form of perfect crystals, but also in roiled grains; and they are obtained partly from alluvial soils and the sands of rivers, and partly from rocks, chiefly a quartzy sandstone or conglomerate, in which they are often associated with gold. A. number of localities in India have long been celebrated as productive of dia monds, particularly Golconda (q.v.); they are found also in Malacca, Borneo, and other parts of the east; nor were any diamonds procured in any other part of the world till the beginning of the 18th c., when they were discovered in remarkable abundance in the district of Serra do Frio, in the province of Minas Geraes, in Brazil. Previous to that
time, diamonds found in Brazilian gold mines had been disregarded as mere pebbles; their nature became known in consequence of some of them accidentally finding their way to Europe. In 1820, they were discovered in the Ural mountains. They have also been found in Rutherford co., North Carolina; in Hale co., Georgia; in the province of Con stantine, Algeria; in Australia; and in South Africa. Diamond mines consist in gen eral of mere diggings and washings of alluvial deposits. In Brazil, the method pursued is to rake the alluvial matter backwards and forwards on inclined planes, over which a stream of water is made to run, till the lighter particles are carried away, when large stones are picked out by the band, and what remains is carefully examined for diamonds. The work is carried on by slaves, and when a diamond of 17 carats is found, the slave who finds it is entitled to his liberty. Large diamonds are comparatively rare among those of Brazil, all the notable diamonds in the world being Indian. Brazil produces yearly from 25,000 to 30,000 carats of diamonds, of which, however, not more than 9,000 carats are capable of being cut, the rest being either very small or of inferior quality. The small and inferior diamonds are called BORT, and command a ready sale for their use in the arts, being pounded in a steel mortar, and much employed in the form of diamond-dust by lapidaries for cutting and polishing diamonds and all kinds of gems, and even for polishing rock-crystals for spectacles. Minute fragments or splinters of bort arc also used for making fine drills, which arc used for drilling small holes in rubies and other hard stones to be employed in watch-making, gold and silver wire-drawing, etc., and for piercing holes for rivets in china, in artificial enamel teeth, etc. The use of small diamonds by glaziers for cutting glass is well known. The diamonds so used arc uncut, and they arc so mounted as to act upon the glass not by an angle, but by a curvi linear edge of the crystal. The cut is only to the depth of about one two-hundredth part of an inch, but is sufficient to make the glass readily break in accordance with it.