Color
Diamonds are also graded by colour, transparent white or the absence of colour being the most sought after. The GIA (Gemological Institute of America) Colour Grading System is the only industry-accepted grading system. Diamonds are graded from colourless to coloured, ranging from white to yellow to brown. The lesser the colour, the higher the value. A code consisting of different letters of the alphabet is used to grade these colours. The scale begins at letter D, representing colourless, and runs through to Z, according to the growing presence of colour.
Diamonds are graded by comparison to preselected diamonds under controlled lighting and precise observation conditions. These slight colour differences greatly affect a diamond's quality and price. Fancy colour diamonds are part of a distinct class and can reach very high value, considering their scarcity and their colour intensity.
The GIA Colour Grading System
Prior to the universalization of the colour classification scale from D to Z by the GIA, another classification system was in place but used letters A, B, and C. In an attempt to avoid any association with the former colour grading system, the GIA eliminated the three first letters of the alphabet and started its classification at D.