Professional Jeweler Archive: The Source of Black

January 2004

Diamonds/Gemology


The Source of Black

New research shows black diamonds' color comes from minerals other than graphite

Black diamonds continue to intrigue consumers newly aware that the hardest gem comes in many colors. To inform consumers interested in what causes the color in these dark stones, gemologists should note new research published in the Fall 2003 edition of Gems & Gemology, the Gemological Institute of America’s quarterly journal.

Scientists from the Russian Academy of Sciences in Moscow, led by Dr. Sergey V. Titkov, analyzed black diamonds from Siberia. The study, which only looked at Russian sources, found magnetite inclusions mainly color the darkest stones, while hematite and iron inclusions color the dark gray stones. These minerals also are responsible for the high magnetic susceptibility of the authors’ samples.

The finding is contrary to previous studies that linked the color in black diamonds to graphite.

  • Gems & Gemology, Carlsbad, CA; (800) 421-7250, ext. 7142, www.gia.edu.
The black diamond shown here was photographed using oblique lighting to show the included crystals in high relief. Courtesy of Nilesh Sheth and Nice Diamonds, New York City; (800) 536-6423. Photo by Robert Weldon.

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