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Revision as of 17:37, 8 October 2005 by 149.123.48.58 (talk)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)The mineral diamond is a crystalline form, or allotrope, of carbon (other allotropes of carbon include graphite, fullerene and ceraphite). It is one of the most known and most useful of more than 3,000 known minerals. Diamonds are renowned for their superlative physical qualities, especially their hardness—the word "diamond" derives from the ancient Greek adamas (αδάμας; "impossible to tame")—and their high dispersion of light. These properties and others make diamond valued for use in jewelry and a variety of industrial applications. Most diamonds are mined from volcanic pipes, where they have been deposited by deep-origin volcanoes drawing material from over 90 miles (150 km) deep within the Earth, where the pressure and temperature is suitable for diamond formation. Most diamonds are mined in central and southern Africa, although significant deposits have also been discovered in Canada, Russia, Brazil, and Australia. About 130 million carats (26,000 kg) of diamonds are mined annually, with a total value of nearly 9 billion US$. In addition, nearly four times that mass is artificially produced as synthetic diamond.
The gemological appeal of diamonds lies in their hardness and optical properties. Diamonds used as gems are cut and polished into a number of faceted shapes in order to accentuate these attractive qualities. The hardness of diamonds allows them to hold a polish extremely well and resist scratching (only other diamonds can scratch a diamond), giving excellent luster. The dispersion of white light into a rainbow of colors, known in the trade as fire, is the other primary characteristic of gem diamonds, and has been highly prized throughout history. Gem diamonds are commonly judged by the four Cs: carat, clarity, color, and cut. Diamonds have been treasured as gems since at least 2,500 years ago, when they were used in religious icons in India. Popularity of diamonds as gemstones increased starting in the 19th century as new cutting designs that display diamonds' gem qualities better were developed.