Dr. Sally Eaton-Magaña, Kgotlaetsho Baatshwana, and Norma-Jean Osi wrote an article about their examination of the 37.41-carat pink and white diamond unearthed in Botswana this summer. It will be published in the next print issue of GIA’s quarterly journal, Gems & Gemology.
Carlsbad, Calif.—The Gemological Institute of America’s laboratory in Botswana recently examined the unique bicolor rough diamond that was recovered from the Karowe diamond mine in August.
The 37.41-carat, Type IIa rough stone measured 24.3 mm × 16.0 mm × 14.5 mm.
Dr. Sally Eaton-Magaña, GIA’s senior manager of diamond identification in Carlsbad, Kgotlaetsho Baatshwana, senior analytics technician at GIA Botswana, and Norma-Jean Osi, an analytics technician at GIA Botswana, used fourier-transform infrared absorption, visible/near-infrared (Vis-NIR) absorption, photoluminescence (PL) spectroscopy, and deep-UV imaging to collect information from the both the pink and colorless sections of the diamond.
The stone showed “mostly a sharp boundary” between the pink and colorless zones, according to an article about the lab’s findings authored by all three.
This image shows the boundary between the diamond’s pink and colorless zones. (Photomicrograph by Wanling Tan; field of view 4 mm)
The two distinct sections indicate that the diamond might have formed at two different times, the lab said.
“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,” Eaton-Magaña said.
“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.”
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Recovered by Lucara Diamond Corp., the bicolor diamond was submitted to the lab for the GIA Diamond Origin Report service.
Pink diamonds are rare and continue to be of scientific interest to the lab.
GIA previously examined comparable Type Ia pink and colorless bicolor rough, both reportedly from Australia, in specimens weighing less than 2 carats each.
According to the article, although the cause of the pink hue has been correlated with plastic deformation, the “precise mechanism and atomic configuration” for the resulting color are topics of ongoing research.
“The distinctive appearance of this bicolor rough diamond displaying two attractive colors, its large size, and its potential to yield more information about pink diamond formation make this diamond quite noteworthy,” the article states.
The article, “Extraordinary Large Bicolor Natural Rough Diamond,” will be published in the next print issue of Gems & Gemology, GIA’s quarterly journal.
