Back to: Diamond Grading Basics
A diamond’s colour is graded with a colour chart; the colour scale goes from D all the way to Z. Starting with D, it is the best, meaning it’s colourless. The colour of a diamond is referring to how much colour is actually in a diamond, the less colour the more expensive the diamond will be. White diamonds are considered colourless; many diamonds will have a slightly yellowish, brownish or greyish colour and will cost less. Diamonds can come in very different colours and these are called Fancy Colored Diamonds. Coloured diamonds are found in nature and in laboratory settings. According to the GIA; only one in 10,000 natural diamonds is a coloured diamond outside the D to Z grading spectrum. Coloured diamonds can be found in almost any shade of the rainbow.
The GIA lists 27 different hues for natural coloured diamonds. Even a one-carat diamond requires billions of carbon atoms to bond, and all those atoms must be carbon to create a colourless diamond. The slightest quirk creates a coloured diamond. The fancy colour scale is used to grade coloured diamonds. It describes the colour of fancy diamonds in these ways: pure spectral colours of diamond (hue) lightness and darkness of the hue (tone) and the colours strength and purity on a scale from neutral to vivid (saturation).
Natural radiation and pressure can intensify the diamond’s colour.
Colour Master Sets
When grading a diamond, professionals compare it with different stones in the master set. First, they identify the two master stones between which the test stone’s colour lies. One is lighter than the test stone, the other darker. They then assign the test stone the colour grade of the lighter master stone.
For example, if a test diamond’s colour lies between G and H, it’s a G colour stone. (G is lighter than H). Remember that the master stone shows the lightest possible colour for its grade. (G has many slightly darker gradations before the colour reaches H).
Table (Face Down) when evaluating diamonds in the normal colour range, professionals place the stones table or face down. They do this because the colour looks more concentrated through the pavilion, and graders look for a lack of colour in these diamonds. In contrast, they grade fancy coloured diamonds table or face up. In these stones, graders look for a maximum amount of colour.
White Light and Neutral Colours
The master set diamonds sit in a white tray shaped like an angular trough that can rock backwards and forwards. The white tray itself sits in a grey lightbox that shines white light on the diamonds. Neutral colours are always used during diamond grading because diamonds reflect the colours around them. So when grading diamonds one should avoid wearing red, yellow, blue, or other bright colours as it will throw off the accuracy of the grade.