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Diamonds are not all truly colorless. Truly colorless diamonds are quite rare.
Most diamonds are nearly colorless with faint yellow or brown tints.
A lettering system from D to Z is used to identify the amount of color present
in a diamond, with D awarded only to the rare, totally colorless stone.
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For reasons not entirely understood, certain diamonds emit a
subtle blue glow when exposed to ultraviolet rays. This interesting phenomenon
is called fluorescence. Many light sources including the sun, fluorescent
office lights, and "black" lights emit ultraviolet rays. In normal lighting
conditions, fluorescence cannot be seen.
The appearance of fluorescence in diamonds exposed to strong
ultraviolet lamps ranges from very faint (barely perceptible) to very strong (a
neon-blue glow). Some diamonds show no fluorescence at all.
With few exceptions, fluorescence in diamonds affects neither
price nor appearance. There are two exceptions to this rule.
In a minute number of cases, diamonds with very strong
fluorescence and a special arrangement of clarity characteristics may look
slightly "cloudy," but consumers rarely encounter such diamonds.
Fluorescence may also have a slightly positive influence on the
appearance of certain off-colored diamonds, thereby making them more desirable
to own.
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Diamonds are graded by their relative lack of color. A diamond
that is said to have "fine color" has little or no coloration. The less the
color, the higher the value.
D-E-F
Colorless.
G-H-I-J
Nearly colorless.
K-L-M
Faintly tinted, usually yellow.
N-O-P-Q-R
Lightly tinted, usually yellow. Tint can be seen with the
naked eye.
S-T-U-V-W-X-Y-Z
Tinted, usually yellow. Tint visible to the naked eye.
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