Diamond Colour
Diamonds come naturally in almost every colour of the rainbow. However, most people prefer diamonds in the white range.
Colourless diamonds are more valuable, because they are rarer and their lack of colour, or whiteness, in a diamond that allows the light to pass effortlessly through the stone and disperse that beauty back to the observer. The colour grading scale established by the GIA (Gemological Institute of America) varies from D (totally colourless) to Z (light yellow). D through F are virtually colourless. G, H and I diamonds appear colourless when mounted. J, K and L diamonds look very nearly colourless, but you can see some colour in larger stones.
Beyond M, most people can see colour pretty easily. The colour of the metal in a mounting can either mask or enhance the diamond colour. Yellow gold makes slightly yellow or brown diamonds appear more colourless. White mounting (gold or platinum) makes the colour more perceptible.
GIA Colour Grading Scale |
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Fluorescence
Fluorescence is not formally a colour grading term. Many diamonds glow when exposed to light which contains relatively high amounts of ultraviolet. This is due to a natural interaction between the light's energy and the atoms in the diamond. Some diamonds (about 10%) fluoresce strongly enough so as to be somewhat noticeable in regular (incandescent) light. Generally, for very light yellow colour diamonds, fluorescence is considered to be beneficial since it makes the diamond appear whiter.
Diamond Education