The name "Diamond" (Diamant French or German, Diamante Spanish or Italian) is derived from the name from the Greek adamas, "unconquerable", referring to its hardness. At one time over 80% of the world's rough diamonds passed through the Diamond Trading Company or DTC, which is a subsidiary of De Beers in London. In the late 1990s, Canadian prospectors discovered several abundant sources of diamonds. The Canadian Ekati Diamond Mine was opened in 1998 and produces 3 million carats of rough diamonds every year. The Diavik Diamond Mine was opened in 2004. Diamonds are mined in alluvial mining operations when they are not located along a kimberlite pipe.
Diamonds are categorized and valued according to the "Four C's" of diamond grading. They are cut, clarity, color, and carat. For more information on this grading system, go to: Diamond Grading - The Four "Cs". The largest diamond ever found was the Cullinan Diamond in 1905.
Diamond has a hardness of 10 on the Mohs scale. The Toughness of Diamond is Good. Diamonds crystallize in the isometric or cubic crystal system, with a "octehedral" crystal habit. Diamond is typically associated with igneous rock kimberlites.
Diamond is a natural allotrope of carbon. The main allotrope of carbon is graphite. The crystal bond structure of diamonds give the stone its hardness and differentiates it from graphite (Diamond Chemistry). Diamond is the hardest natural occurring material. Diamonds are one of the most prized gemstones; however, diamonds have industrial applications as well. Diamond is a transparent, optically isotropic crystal with a specific gravity of 3.52, a refractive index of 2.417, and a high dispersion of 0.044.
Diamonds crystallize in the cubic crystal system and consist of tetrahedrally bonded carbon atoms. The brilliance and luster of diamonds are described as adamantine, which means diamond-like. Some diamonds exhibit fluorescence of various colors (usually blue) under long wave ultra-violet light, but generally bluish-white, yellowish or greenish fluorescence under X-rays. Canadian diamonds, however, show no fluorescence. Diamond is singly refractive (isotropic) with a refractive index of 2.417.
Chemical composition: C
Diamond History
Due to their incredible hardness, diamonds were probably used a cutting or drilling tools, prior to their use in ornamentation. There known use dates back as far as the 4th century BC. Pliny the Elder (23-79 AD) wrote about 'adamas' (diamonds) in his encyclopedia "Historia naturalis," stating: "The substance that possesses the greatest value, not only among precious stones, but of all human possessions, is adamas; a mineral which for a long time, was known to kings only, and to very few of them," adding that diamonds are: "tested upon the anvil, and will resist the blow to such an extent as to make the iron rebound and the very anvil split asunder."
Diamond can be treated in a variety of ways to "enhance" their appearance. Heat and/or irradiation may be used to bring out a certain color or hue. Laser beams can be used to remove tiny imperfections or inclusions. Microscopic passages that are created by the laser beam are then filled with clear resins or glass rendering them invisible to the naked eye. Lasers are also utilized to fill tiny fissures that reach the diamond's surface.
High-Temperature High-Pressure (HTHP) or (GE POL) treatment techniques can also be used to enhance clarity and alter color. Gemological testing laboratories use characteristic inclusions, internal graining and strain patterns to differentiate a lab-treated GE POL diamonds from a natural untreated stones.
Irradiation is used to improve color and brilliance in diamond. Irradiated Diamonds tend to have a greenish cast when viewed under a loupe. Since irradiation is a surface-only tratment, the interior of the stone will appear darker than the outside.
