Chemical composition -- Almost pure carbon, crystallized under extremes of heat and pressure.

Color -- Colorless to yellow, brown, orange, blue, green, pink, black. Most diamonds are slightly yellowish, and in this general color range, those most approaching absolute lack of color are most prized. However, brightly colored diamonds are much rarer and more expensive.

Optics -- R.I. 2.417. Dispersion 0.044 (high).

Durability -- Hardness 10 on Mohs scale. The hardest natural substance. Diamonds can be cut and polished only with other diamonds, and only because of slight directional differences in hardness and a perfect octahedral cleavage. While diamonds are tough, they can be chipped along sharp girdles or facet edges. Diamonds are also highly heat resistant, but they can be burned if subjected to prolonged high heat.

Crystal structure -- Isometric (cubic).

Specific Gravity -- 3.515.

Sources -- The major sources include southern Africa, Australia, and Siberia. In North America, the best known source is at Murfreesboro, Arkansas, although it has not been commercially developed.  Significant deposits have been found recently in Canada.