The diamond is the only gemstone that occurs in all shades of color but the most common colors (after cutting) are from white to yellow. An international rating system from “D” to “Z” was developed for these basic colors. The whiter the shade of the stone, the closer the mark of the stone is to the beginning of the alphabet.
Color specification must be performed by experienced professionals by using a set of sample stones and comparing them with a given stone. Carefully controlled lighting conditions must be used for example, normalized light of 5000/5500 K (D55) and a standard procedure for the classification of the examined stone to the right color grade.
Fancy color are diamonds with intensive coloring.
When the diamond is illuminated by ultraviolet light it can emit visible light on different levels (none – slight – medium – strong). These diamonds are fluorescent.