Diamond Color

A chemically pure and structurally perfect diamond is perfectly transparent with no hue, or color. However, in reality almost no gem-sized natural diamonds are absolutely perfect. The color of a diamond may be affected by chemical impurities and/or structural defects in the crystal lattice. Depending on the hue and intensity of a diamond's coloration, a diamond's color can either detract from or enhance its value. For example, most white diamonds are discounted in price as more yellow hue is detectable, while intense pink or blue diamonds (such as the Hope Diamond) can be dramatically more valuable. Out of all colored diamonds, red diamonds are the rarest of all.

Diamonds occur in a restricted variety of colors — steel gray, white, blue, yellow, orange, red, green, pink to purple, brown, and black. Colored diamonds contain interstitial impurities or structural defects that cause the coloration, whilst pure diamonds (which are exceedingly rare) are perfectly transparent and colorless. Diamonds are scientifically classed into two main types and several subtypes, according to the nature of impurities present and how these impurities affect light absorption:

The Gemological Institute of America (GIA) uses a "D" to "Z" scale it developed for grading the color of "white" (non-fancy colored) diamonds, where "D" is colorless and "Z" is yellow:

• colorless: D, E, F
• near colorless: G, H, I, J
• faint yellow or brown: K, L, M
• very light yellow or brown: N, O, P, Q, R
• light yellow or brown: S, T, U, V, W, X, Y, Z

Other diamond grading agencies, notably the European Gemological Laboratory (EGL) and the American Gemological Society (AGS), also use the color scale developed by the GIA.

Diamonds that rate toward the colorless end of the range are sometimes known as "high-color" diamonds, and those toward the other end, "low-color" diamonds. These terms refer to the relative desirability (as demonstrated by market prices) of color grades, not the intensity of the color itself.

Diamond color is graded by comparing a sample stone to a master set of diamonds with colors defined as "D" through "Z". Diamonds having a color more intense than "Z" are considered fancy colored diamonds, and can be graded using separate systems which indicate the characteristics of the color, and not just its presence. These color grading systems are more similar to those used for other colored gemstones, such as ruby, sapphire, or emerald, than they are to the system used for white diamonds.

Diamonds that enter the Gemological Institute of America's scale are valued according to their clarity. For example, an "E" rated diamond (colorless) is much more valuable than a "Y" rated diamond (light yellow or brown). This is due to two effects: high-color diamonds are rarer, limiting supply; and the bright white appearance of high-color diamonds is more desired by consumers, increasing demand. Poor color is usually not enough to eliminate the use of diamond as a gemstone: if other gemological characteristics of a stone are good, a low-color diamond can remain more valuable as a gem diamond than an industrial-use diamond.

Diamonds that go out of scale in the rating are known as "fancy color" diamonds. These diamonds are valued using different criteria those used for regular diamonds. When the color is rare, the more intensely colored a diamond is, the more valuable it becomes. Fancy-colored diamonds such as the deep blue Hope Diamond are among the most valuable and sought-after diamonds in the world