diamond: Sources
Sources
The earliest sources of gem diamonds were India and Borneo, where they were found in river alluvium. All famous diamonds of antiquity were Indian diamonds, including the Great Mogul, the Orlov, the Koh-i-noor, and the Regent or Pitt. Other famous diamonds are the Hope (blue), Dresden (green), and Tiffany (yellow). In the early 18th cent., deposits similar to those in India were found in Brazil, mainly of carbonados, though they may have been known as early as 1670. In 1867, a stone found in South Africa was recognized as a diamond. Within a few years, this began a wild search for diamonds, both in river diggings and inland. In 1870–71, dry diggings, including most of the celebrated mines, were discovered. Well-known South African diamond mines are the Dutoitspan, Bultfontein, De Beers, Kimberley, Jagersfontein, and Premier. Russia, Botswana, Congo (Kinshasa), Australia, and South Africa are now the world's major diamond-producing nations; other important countries include Canada, Angola, Namibia, Ghana, and Brazil. The use of diamonds to finance African rebel groups and fuel civil strife led, in 2001 and 2002, to international agreements (the Kimberley Process) designed to certify legitimately mined diamonds, but in 2011 the permitted sale of diamonds from Zimbabwe, where the army has been accused of brutality and human rights violations in diamond mines and diamond revenues support an autocratic government, led to criticism of the certification process.
Synthetic diamonds were successfully produced in the early 1950s; a number of small crystals were manufactured when pure graphite mixed with a catalyst was subjected to pressure of about 1 million lb per sq in. and temperature of the order of 5,000℉ (3,000℃). Synthetic diamonds are now also commercially produced at a lower pressure in a process that heats methane and hydrogen gas into a plasma in a vacuum chamber; the diamond is built up in layers from a substrate through the deposition of vaporized carbon from the methane. Microscopic diamonds also have been produced through other means, including the detonation of explosives containing carbon. Synthetic diamonds are now extensively used in industry, and are also used as gemstones in jewelry.
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