What is 'Colour Grading'

The colour grading system of diamonds is based on how colourless they are for white diamonds, or their spectral hue, purity and intensity of colour for fancy coloured diamonds. The three internationally recognized gem grading laboratories GIA, HRD and IGI all use a grading system where D is the highest (most colourless) and Z the lowest (yellowish) colour. Evidently this system is for white or colourless diamonds only. Grading fancy coloured diamonds usually starts with identifying the colour and then grading its intensity.

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