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Article: diamond
- Article from:
- The Columbia Encyclopedia, Sixth Edition
CopyrightThe Columbia Encyclopedia, Sixth Edition. Copyright 2008 Columbia University Press. (Hide copyright information)
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diamond mineral, one of two crystalline forms of the element
carbon
(see
allotropy
), the hardest natural substance known, used as a gem and in industry.
Properties
Diamonds crystallize in the isometric system (see
crystal
) commonly as transparent to translucent white, colorless, yellow, green, blue, or brown octahedrons (the familiar diamond shape). The extraordinary brilliancy of diamonds after faceting is due to their very high refractive index, which is greater than that of any other naturally occurring gemstone. In addition to the
gem
varieties there are bort, which is poorly crystallized or of inferior color and in fragmentary condition, and carbonado (black diamond), ...