A diamond is graded to determine its relative absence of color, based on the GIA Color Scale which ranges from D (colorless) to Z (light yellow to brown). GIA assigns a color grade by comparing each diamond to a master set in a highly controlled lighting and viewing environment.
The color evaluation of most gem-quality diamonds is based on the absence of color.
A diamond’s value is often affected by the rarity of one or more of the 4Cs. Colorless diamonds are scarce— most diamonds have tints of yellow or brown. A chemically pure and structurally perfect diamond has no hue, like a drop of pure water, and consequently, a higher value. Value and rarity are related: in this case a colorless diamond is more rare and more valuable than one with a slight yellow color. The same relationship between rarity and value also exists for carat weight, clarity and cut.
GIA’s D-to-Z diamond color-grading system measures the degree of colorlessness by comparing a stone under controlled lighting and precise viewing conditions to masterstones stones of established color value.
GIA’s diamond D-to-Z color-grading scale is the industry’s most widely accepted grading system. The scale begins with the letter D, representing colorless, and continues, with increasing presence of color, to the letter Z.
Many of these color distinctions are so subtle that they are invisible to the untrained eye; however, these distinctions make a very big difference in diamond quality and price.
Why does the GIA color grading system start at D?
Before GIA universalized the D-to-Z Color Grading Scale, a variety of other systems were used loosely; from A, B, and C (used without clear definition), to Arabic (0, 1, 2, 3) and Roman Numerals (I, II, III), and even descriptive terms like “gem blue” or “blue white,” which are notorious for misinterpretation. So the creators of the GIA Color Scale wanted to start fresh, without any association with earlier systems. Thus the GIA scale starts at the letter D. Very few people still cling to other grading systems, and no other system has the clarity and universal acceptance of the GIA scale.
Are Zs considered fancy-color?
No. Naturally colored diamonds outside the normal color range are called fancy-color diamonds. The FTC (Federal Trade Commission) provides no guidelines for the use of the term “fancy-color” in the US, but there is general agreement in the international trade that fancy-color diamonds are either yellow or brown diamonds that have more color than a Z masterstone or they exhibit a color other than yellow or brown.
Our next blog post will focus on the final and arguably most important of the 4Cs; CUT!