Diamond

Diamond is a transparent, optically isotropic crystal with a refractive index of 2.417, a high dispersion of 0.044, and a specific gravity of 3.52. Sometimes known as adamant, it is the hardest known naturally occurring material, scoring 10 on the old Mohs scale of mineral hardness. The diamond derives its name from the Greek adamas, "untameable" or "unconquerable", referring to its hardness.

The lustre of a diamond is described as adamantine, which simply means diamond-like. Diamonds exhibit fluorescence of various colors under long wave ultra-violet light, but generally bluish-white, yellowish or greenish fluorescence under X-rays. Diamonds have an absorption spectrum consisting of a fine line in the violet at 415.5 nm. Colored stones show additional bands. Brown diamonds show a band in the green at 504 nm, sometimes accompanied by two additional weak bands also in the green.

Diamonds are valued according to the four C's of diamond grading, namely cut, clarity, color, and carat. Both rough and cut diamonds are graded and separated based on these four characteristics at a number of heavily guarded grading centers around the world.

Diamonds occur in a variety of colors - steel, white, blue, yellow, orange, red, green, pink, brown and black. Colored diamonds contain impurities or molecular defects that cause the coloration, whilst pure diamonds are always transparent and colorless.

Colorless diamonds are priced higher than yellow diamonds. However, when a diamond's color passes a certain intensity, it enters the realm of "Fancy Color". In this case, the intensity of the color in the diamond plays a major role in its value. The value of a Fancy Color Diamond may far surpass that of colorless diamonds, if the intensity of the color is high and the color is rare. Fancy diamonds come in all colors of the rainbow. A fancy brown diamond may have low value, relative to colorless diamond. However, a fancy pink or blue diamond will command higher prices.