Diamond color education...

Diamonds with an absence of body color most purely reflect the full color spectrum and are therefore the most valuable. Most diamonds come in a wide range of colors and are graded on a letter scale from D (colorless), the highest grade, through Z (usually a light yellow, brown, or gray). It is difficult for the untrained eye to see variations in color grades D through J unless stones are being compared side by side.

Diamonds should be color-graded under exacting conditions by an expert grader using specially filtered cool white light. They should be compared to a set of diamonds with known colors, graded by the Gemological Institute of America against their master set.

To obtain the most accurate color grade, graders usually place diamonds on their sides or upside-down against a neutral background, to help reduce the play of spectral colors that diamonds reflect.


Question

What is Fluorescence?
Fluorescence is the natural phenomenon that causes some diamonds to glow when exposed to an ultraviolet light source. Usually this glow has a blue color, but other colors are possible. Fluorescence is noted as Nil, None or Negligible if there is no reaction under ultraviolet light, or Faint, Medium, Strong, or Very Strong. Strong or Very Strong fluorescence is usually less desirable in higher color grades, such as D, E, and F. However, if a diamond has Very Strong blue fluorescence, this can be desirable in a lower color grade such as J or K, as the glow may make the diamond appear brighter. Unless the fluorescence is in the Strong or Very Strong range, which might affect the price of a diamond in a higher color grade, fluorescence does not have a major impact on diamond value and should be weighed against other factors.

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