Di´amond, the hardest and one of the most valuable of gems, and the purest form in which the element carbon is found. (See Carbon.) It crystallizes in forms belonging to the regular or cubic system, the most common being the regular octahedron and rhombic dodecahedron (twelve faces). The finest diamonds are colourless, perfectly clear, and pellucid. Such are said to be of the finest water. But diamonds are often blue, pink, green, or yellow, and such are highly prized if of a decided and equal tint throughout. The hardness of the diamond is such that nothing will scratch it, nor can it be cut but by itself. The value of a diamond is much enhanced by cutting facets upon it inclined at certain angles to each other so as to produce the greatest possible play of colour and lustre. What is called the brilliant cut best brings out the beauty of the stone. Its upper or principal face is octagonal, surrounded by many facets. But this form of cutting requires an originally well-shaped stone. For other diamonds the rose cut is used. In this form six triangles are cut on the top so that their apices meet in a point called the summit. Round this are disposed other facets. Stones which are too thin to cut as rose-diamonds are cut as table-diamonds, which have a very slight play of colour. In the cut, fig. 1 is the diamond in its rough state; fig. 2 is the vertical, and fig. 3 the lateral appearance of a brilliant; fig. 4 the
vertical, and fig. 5 the lateral appearance of a rose-cut diamond; in fig. 6 the flat portion a in a cut stone is called the table; the part a b b, which projects from the setting, is the front, the part b b c, sunk in the setting, is the back or culasse, while the line b b is the girdle. The art of cutting and polishing the diamond was unknown in Europe till the fifteenth century, and the stone itself was not nearly so highly valued in the Middle Ages as the ruby. Diamonds are valuable for many purposes. Their powder is the best for the lapidary, and they are used for jewelling watches, and in the cutting of window- and plate-glass. When used as a glazier's tool the diamond must be uncut. Inferior kinds of diamonds are also extensively used by engineers in rock-boring, and by copperplate engravers as etching-points. Diamonds are obtained from deposits of various kinds, mostly alluvial (sands, clays, &c.), being separated by washing. They have been found in India, Borneo, and other parts of the East; sometimes in N. America and Australia; Brazil has produced large numbers; but the chief diamond-field of to-day is in Cape Province, the centre being Kimberley. Diamonds were discovered here in 1867, and since then the output has amounted to over £183,000,000 in value. The diamonds are no longer obtained by mere surface workings, but the excavations have been carried down to a depth of 2000 feet. 'River diggings' are also carried on on the banks of some of the rivers. Some of the S. African diamonds are very large. One of them, the Cullinan diamond, discovered in 1905, is a monster of 3025 carats, of very good colour, being by far the largest diamond known. A celebrated diamond is the Koh-i-noor (Mountain of Light), an Indian stone belonging to the British crown. Its history extends over five or six centuries. It weighed at one time 280 carats, but by cutting has been reduced to about 106 carats. The Orlov diamond, which belonged to the Emperor of Russia, weighed 194 carats; the Pitt diamond, among the French crown jewels, weighs 136½ carats.—Bibliography: A. Jeffries, A Treatise on Diamonds and Pearls; H. Emanuel, Diamonds and Precious Stones; E. W. Streeter, Precious Stones and Gems; idem, The Great Diamonds of the World; G. F. H. Smith, Gem-Stones; P. A. Wagner, The Diamond Fields of Southern Africa.
Diamond-beetle, Entimus imperialis, a handsome South American insect belonging to the family Curculionidæ or weevils. It is spangled with golden-green on a black background.
Diamond Harbour, a port on the left bank of the Hugli River, about 38 miles by the railway from Calcutta, formerly much used as an anchorage for ships waiting for the tide.
Diamond Lore. In Hellenic, Arabian, Chinese, and other literature the diamond is connected with the eagle and snakes. Diamonds, according to ancient belief, lie in deep valleys infested by snakes, or entirely surrounded by straight, high cliffs. Pieces of flesh are thrown down and eagles seize them. The birds are followed to their nests, where the diamonds that adhered to the flesh are found. Mixed with this legend is the older one regarding the 'eagle stone', which assists parturition. It was believed a woman was easily delivered if the 'eagle stone' were placed on her abdomen. The Chinese legend was imported with the diamond from Fu-lin (Syria). Indian diamond lore is mixed with pearl lore. According to the Buddha birth stories, diamonds are found in the sea. The ancients asserted that the diamond could not be injured by iron, fire, or smoke. Before it could be broken it had to be steeped in ram's blood. The alchemists used lead as a substitute for ram's blood. In Chinese lore diamonds are rulers of gold and have their origin in gold. A similar belief prevailed in mediæval Europe, adamantine gold being credited with the same virtues as the diamond. Both gold and the diamond were sacred. The diamond is a mediæval symbol of Christ; in the Far East it is connected with Buddha. The association of the diamond with snakes gave origin to the belief that it was poisonous, the saliva of the snakes clinging to it. Diamond dust is regarded in India as a deadly poison. Like the sacred pearl, the diamond has been credited with nocturnal luminosity. Certain varieties of diamonds when heated, rubbed, or exposed in bright sunshine emit slight rays of light for a short time in darkness. The belief in 'night shining gems', however, had origin in pearl lore, the pearl having been connected with the moon ('the pearl of heaven'). Coral, rhinoceros-horn, fern seed, the mandrake, &c., were likewise connected with the moon-goddess and credited with nocturnal luminosity.
Diamond Necklace, an affair of some note in French history immediately preceding the Revolution. See Marie Antoinette; La Motte; and Rohan, Louis.
Dian´a, in Roman mythology, an ancient Italian goddess, in later times identified with the Greek Artĕmis, with whom she had various attributes in common, being the virgin goddess of the moon, and of the chase, and having as attributes the crescent moon, bow, arrows, and quiver. The name is a feminine form of Janus. She seems to have been originally the patron divinity of the Sabines and Latins. She was worshipped especially by women, as presiding over births, no man being allowed to enter her temple.