Most diamonds contain some hint of color. This is caused by the presence of nitrogen, crystal structure, and other trace elements in the earth where they are formed. Color grading for most diamonds is done on a scale of D to Z. This scale is used for all diamonds that are colorless or are yellow, brown or grey. A diamond with more color than a Z, or any color other than yellow, brown or grey is a ‘fancy colored’ diamond. These ‘fancy colors’ are not graded on the same scale.
Common Grading Standards
Many grading labs are more focused on volume than adhering to strict grading standards. These labs have a tendency to be very soft on varying aspects of diamond grading. This is especially true when it comes to color grading. Lax standards in color grading can give the buyer a false or negative impression about the appearance of a diamond that has been graded using stricter standards. Diamonds that have been graded by these relaxed standards are often carried by chain stores, mall and discount outlets, and “wholesalers”. In some cases, the labs being used are wholly or partially owned by the stores that are selling the diamonds. This factor totally voids any benefit of buying a diamond with a report from that lab.
AGS and GIA Standards
The world’s most notable diamonds are sent to the Gemological Institute of America (GIA) and American Gem Society (AGS). These labs employ strict and consistent standards. Diamonds with AGS and GIA reports command a higher premium and hold their value better than diamonds from softer labs.
Cut Influences Color
Diamonds in the D-Z scale are graded face-down, viewed through the side of the pavilion. This is because shape and cut quality both influence how light gets in and out of the diamond; grading face-down allows for a neutral assessment of body color. The brilliant cutting style is most efficient for returning light, so a round brilliant or princess may show less apparent color face-up than a step cut like an emerald or Asscher.
Above-Average Cut Quality
When cut quality is above average brilliants can “face up” with notably less color than the AGS or GIA color grade they were assigned, which was determined face-down. Why? Because light gets in and out faster. This is the opposite of poor cutting (or cutting for colored stones) where critical angles are missed and light rays escape through the pavilion or make multiple bounces before leaving – which illuminates body tone. The more superior the cut quality is the less color is seen face-up.