Diamonds can occur in virtually all colours of the spectrum, as well as milky-white, black and grey. The two most commonly occurring colours, or hues, in diamonds are yellow and brown with yellow being by far the most prevalent. Some colours are very rare, the rarest and most highly prized colour of all being that of red diamonds.
Coloured diamonds are graded according to their properties of hue (spectral colour), tone (lightness or darkness) and saturation (intensity). In all cases, for any given hue, the greater the saturation the higher the value.
The GIA, recognised as the foremost authority on the grading of coloured diamonds, currently grades colour in nine different categories ranging from Faintly Coloured to Fancy Vivid Colour. Argyle Pink Diamonds, Argyle Champagne Diamonds and Argyle Cognac Diamonds are graded according to a proprietary, in-house system developed by the Argyle Diamond Mines of Australia.
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