The 4 Cs
colour
clarity
cut
carat weight
Diamond professionals use these four factors to describe and classify diamonds. When taken together, they help in evaluating the finished diamonds you buy. That's why they are often called value factors. This page considers colour.
You may wish to view the excellent tutorial on the Gemological Institute of America web site titled How to Buy A Diamond
colour
When applied to diamonds, colour is often misunderstood by people outside the diamond trade. Many people think of diamonds as colourless. In reality, truly colourless diamonds are quite rare. Most diamonds used in jewellery are nearly colourless with faint yellow or brown tints. These diamonds fall in the normal colour range.
Why does the GIA colour grading system start at D?
Before GIA introduced the GIA D-Z Colour Grading Scale, a variety of other symbols were loosely applied throughout the industry. Not only were A, B, and C used without clear definition, but some dealers, taking a cue from the poultry business perhaps, started grading their diamonds double A (AA). Other systems used numbers—both Arabic (0, 1, 2, 3) and Roman (I, II, III). Most dubious of all were systems that relied on descriptive terms like "gem blue" or "blue white." Terms like these are notoriously susceptible to misinterpretation. So the creators of the GIA Colour Scale wanted to start fresh. They wanted symbols that would not have any association with earlier systems. Thus the GIA scale starts at the letter D. There may be some people still clinging to other grading systems, but no other system has the clarity and universal acceptance of the GIA scale.
Diamonds outside the normal colour range are called fancy-coloured and come in about any colour you can imagine.
Diamonds in the normal range are graded and evaluated by how closely they approach absolute colourlessness. Most diamonds sold in the retail trade run from very nearly colourless to slightly yellow or brown, the normal range. The Gemological Institute of America divides diamonds in the normal range into grades ranging from D = Colourless through to Z = very light yellow or brown. Diamonds with more colour than Z are referred to as "Fancy" colours.
Why does the GIA colour grading system start at D?
Before GIA introduced the GIA D-Z Colour Grading Scale, a variety of other symbols were loosely applied throughout the industry. Not only were A, B, and C used without clear definition, but some dealers, taking a cue from the poultry business perhaps, started grading their diamonds double A (AA). Other systems used numbers—both Arabic (0, 1, 2, 3) and Roman (I, II, III). Most dubious of all were systems that relied on descriptive terms like "gem blue" or "blue white." Terms like these are notoriously susceptible to misinterpretation. So the creators of the GIA Colour Scale wanted to start fresh. They wanted symbols that would not have any association with earlier systems. Thus the GIA scale starts at the letter D. There may be some people still clinging to other grading systems, but no other system has the clarity and universal acceptance of the GIA scale
