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Colour |
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Colours are described by three factors:
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Hue, (red, green, blue, etc.)
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Saturation, (strong or pastel, red or pink.)
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Tone, (light to dark.)
Generally speaking, highest values go to stones with pure hues and strong rich colours. With high value gems, subtle variations make a significant difference in price. For example, a slightly organic ruby will not be worth nearly as much as one that is pure red. Most people cannot see the difference, but to the expert grader it is significant. On moderate priced gems, colour has less affect on value. For example, tourmaline comes in every possible color. Unless it is an exceptionally pure green, red or pink, they are all about the same value. It is the other factors of size; clarity and cutting that determine the gem's value.
Diamonds are graded on how close they are to being colourless. There are three grades of "colourless" that only vary by subtle differences in transparency. Then there are four grades of "white." These are gems that will appear colourless when set in jewelry. It takes an expert in a laboratory setting to distinguish between these grades, but each represents a change in value.
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