DIAMOND (OF., Fr. diamant, H.. Sp. dia la ante, from Lat.' a dania R, adamant, from Gk. tidcipac, adamas. adamant. from a. a prig. dajair, (lumen. Ski. dam, to subdue). A preeious stone composed of pure carbon, remark able for hardness. lustre. and flash of color. It crystallizes in the isometric system, usually in octahedrons, or in combinations of several forms, including the octahedron, cube. rhombic dode cahedron. trisoetahedron. and hexoetahedron: the faces and edges of the crystals frequently are curved. It has a very perfect cleavage, by which the primary form of the octahedron may be derived. The diamond is not acted upon by acids or alkalies. but if heated to a high temperature in the presence of oxygen it burns to carbon dioxide. Its brilliant lustre and display of prismatic colors are due to the property of re fracting and dispersing the light-rays, a property possessed in the highest degree by colorless stones. The specific gravity of the diamond is 3.52 ; its hardness, which is assumed to be 10 on the mineral scale, exceeds that of any other known substanee. Ily friction it becomes phosphoreseent and positively electric. The diamond has a great variety of natural colorings; white. yellow. and brown specimens are the most common, but pure white and fine shades of brown a nil yellow are quite rare and command high prices, lied in rich, sleep tints is perhaps the most prized of all colors. while blue and green are also highly val ued owing to their beauty and rarity. 'lice amorphous steel-gray to black diamond. known as 'bort• or 'carbonado.' which is unsuitable for gems. is extensively used on the cutting edge of drill. for tunneling and prospecting.
(Wei linE: E. l'reviCILIs to the discovery of the Brazilian mines in 1727. diamonds were found chiefly in India and Borneo. In India they have been obtained near liadapa, 1:.arnul. and Bell: ri in Madras Presidency; near Nagpur. in the Central Provinces; and at Palma. in Blank'. khand. The Oolconda was a market in Madras Presidency where the diamonds were col lected from the mines. Formerly the diamond mining industry gave employment to a large number of reople. lout. owing to the gradual ex haustion of the deposits and the crude methods of Nvorking. it has steadily declined. The diamond mines of litcrile.c. which supply about 3000 carats annually. are located in the we-tern part of the island near Pontianak. The Brazilian diamonds come from a small district within the States of Bahia. 'Minas Oeraes, and Matto Grosso, hying for the Most part in placers. Dia Ilagagem. and -thaete in .)Minas Oerae: are the principal localities for geumstones. and Leiceocs, Sincor:i. and Santo Ignacio for carbo nado:. The alluvial deposits consist of water worn quartz pebbles, and ferruginous clay. car rying rutile, hematite, ilm•nite, and other minerals besides the diamonds. In one locality I Bagagem) the stones are found in a weathered, decomposed phyllite; they are also known to oc cur elsewhere in conglomerate. The total output
of the Brazilian mines up to the year 1899 has been estimated by one authority at 13,103.000 carats. The most valuable specimen front this source is the "Southern Star." found in 1S5-1, which weighed 254 carats in the rough. and 124 carats after cutting. The South Afriean dia montl-tields yield about OS per cent. of the total product. Their discovery in 1Sti; came from the purchase of a stone that had been picked up by the children of a Boer farmer. and which was subsequently sold in Paris for $2500. The dia mond: are found in both river diggings and dry diggings. Myer diggings occur along the Vaal liver from Potchefstroom down to the conflu ence with the Orange, and up the latter river as far as Hopetown. is conducted in a similar manner to gold-washing. the operations usually being on a limited scale. The dry dig gings are in Oriqualand West, on the borders of the Orange River Colony. about 1140 miles north east of Cape Town. 'limy comprise a number of small areas of circular or oval form. ranging in diameter cup to one-fourth of a mile. Origi Lally the areas were divided into small each owned and operated independently, but they are now worked by a single company. the Do Beers Consolidated .11ines. Limited, whose head quarters arc at Kimberley. The unities are opened on a large scale, and yield enormous prolits. It is stated that the output from ISII7 to 1S97 was over 33.on0.nn0 carats. or about 71:, valued after at ::4150.000.000. in the fiscal year 1901 the De Beers Company received from sales of rough dia The South African diamonds in the average do not equal the Brazilian for purity. although some 111 the valuable stones, re markable for quality as well as for sire. hive been found in these mines. Other countries where din aid s Is flown to oeefir a re the States, British Ouiana, Russia, China. Sumatra.
and Australia. In the United States there are no deposits. so far as discovered, of sullicient value to warrant mining operations, the stones being found only occasionally in alluvial mate rials and drift. 3.1ore than fifty specimens have been identified, of which the largest, weighing nearly 24 was found at •lanchester. iu 1S53. Their occurrence is generally confined to the regions of the southern Appalachians. the Oreat Lakes. and to the Coast and Sierra Nevada ranges of California and oregon. The diamond-fields of British Cuiana are about Irol miles up the Mazaruni Biver, and. while new, they give some promise of future importance. New South Wales produces about 2.3,000 carats annually from alluvial washings near .Nludgee, and on the Alacpmrie River. In Russia. dia mond: occur on the western slope: of the Ural:. and are obtained in the washing of sands and gravels for gold.