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Color Grading Scale

The Color Grading Scale: ranges from totally colorless to fancy yellow.
The differences between one grade and another are very subtle,
as can be seen by the number of grades within any one category.

Diamonds are graded for color only as loose, unmounted stones in the inverted position (table down, pavilion up),
and under very specific conditions of lighting and background,
and also the distance and angle of the observer in relation to the stone.
A color scale has been devised by the Gem Trade Lab. of the Gemological Institute of America (GIA)
divided alphabetically from D (the absence of color) to Z (fancy yellow color), and is recognized world-wide.
Each letter grade represents a small range of color, and not just a single color.
Diamonds are color graded by being compared to a set of master stones.

D E F Colorless
G H I Nearly colorless (not distinguishable from colorless when mounted)
J K L Slightly yellow (color distinguishable to the trained eye)
M N O Light yellow
P Q R S T U V W X Darker yellow
Z Fancy colors

Even though there are several grades in each category, there are slight differences between the letter grades.
D is the clearest and most valuable, X is a dingy yellow and least expensive.
Z grade-colored diamonds are the rarest and most expensive.
A diamond so saturated with nitrogen that it becomes a deep, rich yellow is as rare as a colorless diamond.

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