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Color Grading Fancy Colored Diamonds

The color grading standards for white diamonds don't apply to fancy colored diamonds. Learn the GIA and Argyle grading systems and how to find signs of artificial coloration.

10 Minute Read

Inform Your Customers About Diamond Colors and Heat

First, some advice. Please tell your customers that some diamonds, particularly green ones, may change color if heated by a jeweler’s torch. This applies to both natural and artificially irradiated diamonds. Since this color change is permanent, recommend they ask jewelers to remove mounted colored diamonds before making jewelry repairs.

Distinguishing Natural from Enhanced Diamond Colors

Approximately one third of all colored diamonds have artificially induced colors. Typically, determining if the color is natural or artificial falls outside the range of standard gemological instruments. This requires sending the diamonds to a major lab. Occasionally, you can determine precisely that the color is artificial. However, you can never determine with certainty if the color is natural. You should send any colored diamonds of significant value to a major lab for testing.

Identifying Irradiation

Exposure to natural radiation in the Earth often affects diamond color. After mining, exposure can also alter color. Artificial radiation treatments usually produce green, blue, or blue-green diamonds. If annealed, these gems can yield pink, red, yellow, orange, and blue colors.

Ion Implantation

Ion implantation is a new, closely related process for coloring diamonds. Ions have a…

Donald Clark, CSM IMG

The late Donald Clark, CSM founded the International Gem Society in 1998. Donald started in the gem and jewelry industry in 1976. He received his formal gemology training from the Gemological Institute of America (GIA) and the American Society of Gemcutters (ASG). The letters “CSM” after his name stood for Certified Supreme Master Gemcutter, a designation of Wykoff’s ASG which has often been referred to as the doctorate of gem cutting. The American Society of Gemcutters only had 54 people reach this level. Along with dozens of articles for leading trade magazines, Donald authored the book “Modern Faceting, the Easy Way.”

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