The GIA laboratory in Botswana recently examined an extraordinary pink-and-colorless bicolor rough diamond. Reportedly from the Karowe mine, the source of several notable diamonds, including the 2,488 ct Motswedi diamond, also examined by GIA, the 37.41 ct rough diamond has distinct colorless and pink sections, possibly indicating that the diamond formed at two different times.
‘It is generally understood that pink color in diamonds results from significant stress causing a change in the diamond’s crystal structure known as plastic deformation,” said Dr. Sally Eaton-Magaña, senior manager of diamond identification at GIA in Carlsbad, California. “The pink section likely was initially colorless and then plastically deformed, perhaps by a mountain-forming event millions of years ago, resulting in its pink color, with the colorless section forming at a later time.”
An article analyzing the bicolor diamond by Dr. Eaton-Magaña, Kgotlaetsho Baatshwana (senior analytics technician), and Norma-Jean Osi (analytics technician), both at GIA in Gaborone, Botswana, is available on GIA’s website with photos and a video. The article will be published in the next print issue of the Institute’s quarterly journal, Gems & Gemology.
Rough pink diamonds are rarely found, and although the cause of color has been correlated with plastic deformation, the precise mechanism and atomic configuration for the resulting color are topics of continuous research.
Therefore, when GIA receives a diamond with distinct pink and colorless sections, it is of scientific interest, particularly at an astounding weight of 37.41 ct. GIA has previously examined comparable type Ia pink and colorless bicolor rough, both reportedly from Australia, in much smaller specimens weighing less than 2 ct each (Spring 2021 Lab Notes, pp. 53–55)
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