Diamond is a transparent crystal composed of carbon atoms. A perfect white diamond is like a drop of sparkling water. Chemical impurities and structural defects add color to the transparent crystal. A structurally perfect and chemically pure diamond is extremely rare to find. Colorless diamonds act like prisms, separating white light passing through it into a wide spectrum of colors, causing a scintillating effect called fire which gives a diamond its mesmerizing appeal. The whiter the diamond, better the fire. While most colorless diamonds appear white, implicitly all display perceptible tints of color. Color grading for colorless or white diamonds involves deciding how closely a stone's body color approaches colorlessness. Color is most accurately determined when the stone is not mounted in a setting, since metals can extend tints of their own color into the diamond. To judge a diamond's color, diamond is placed face down on a pure white surface and examined in controlled light.
Note : Diamonds with noticeable tints of color are referred to as fancy colored diamonds or natural colored diamonds. Colored diamonds occur in a variety of hues including pink, red, violet, orange, purple, yellow, brown, green, black and blue. Fancy colored diamonds are extremely rare, valuable and serve a niche segment.
Although color grading for diamonds has existed since ages, the turn of 19th century has seen more standardization in the color gradation process of diamonds. The diamond color grade standards set by the following two organizations are well revered and recognized in the industry.
1. Gemological Institute of America (GIA)
First laboratory in the world to address the aspects of color grading for diamonds. Grades color on an alphabetical scale of D to Z.
2. American Gemological Society (AGS)
Grades diamonds' color on a numeric scale of 0 to 10.
GIA's alphabet grade has a universal appeal. The scale begins with the highest rating of D for colorless, and travels down the alphabet to grade diamonds with traces of very faint yellowish or brownish hue. The AGS Color Grade indicates where a diamond's color falls on a numeric scale that runs from 0 (colorless) to 10 (light yellow or light brown) in 0.5 increments.
Fluorescence is defined as a diamond's tendency to emit a soft colored glow when exposed to long-wave ultraviolet light (such as the lighting frequently seen in dance clubs) or fluorescent light (such as the lighting frequently seen in a showroom). Most fluoro diamonds fluoresce a blue glow which gives a whiter appearance to the diamond similar to the bluing liquid that makes white laundry even whiter. In very rare cases though, strong fluorescence in a high color grade diamond may make the diamond appear foggy or oily. Fluorescence in lower color grade diamonds enhances the appearance of the diamond making the stone a great value-for-money purchase.
Fluorescence is a complex phenomenon that is more debated than understood. Consumer attitude over fluorescence varies. While some people are prejudiced against fluorescence, many actually enjoy the effect. It is a matter of what appeals to the aesthetics. And the fact fluoro diamonds may cost less is a real bonus.