Diamond, a hard, crystalline form of carbon. Diamonds are valued both for their beauty as gems and for their industrial uses. They are typically colorless, but may occur in tints of blue, green, black, brown, light yellow, orange, or pink. Most diamonds have an eight-sided crystalline structure. The diamond is the birthstone for April, and is a symbol of innocence.

Diamond is the hardest natural substance known, and it will not dissolve in any known solvent. It conducts heat much better than any other material, including metals. When ignited in oxygen at a temperature of 1,600 F. (870 C.) or more, it will burn.

Diamonds occur in many parts of the world and are also produced synthetically. Synthetic diamonds have been produced since the 1950's. They are virtually identical to natural diamonds, but, because of the expense of their manufacture, are usually produced only in small sizes suitable for industrial use. In the 1980's, a process was developed for producing a very thin film of diamond on other materials.

Diamonds are weighed by the carat. One carat is equal in weight to 200 milligrams, or approximately 0.007 ounce.