The GIA analysed the 1.10-carat, fancy deep brownish orangey pink diamond at its New York laboratory, as reported in the fall issue of Gems & Gemology. The diamond showed a ‘mottled’ appearance, said to be an uncommon feature in treated pink diamonds.
Analysis found the diamond underwent high-pressure high-temperature (HPHT) annealing, irradiation, and moderate heating. These treatments formed nitrogen-vacancy (NV) centres that produced the pink colour.
Furthermore, microscopic examination revealed the mottled pattern extended from just below the surface to the polished surface. Visible and near-infrared (Vis-NIR) light spectroscopy identified features consistent with laboratory irradiation and heat treatment.
"After formation within the earth, the crystal structure of a diamond can be subjected to plastic deformation, which can impart a brown colour to the crystal," the GIA report explains.
"Such plastic deformation may have contributed to the mottled pattern observed on the diamond, with the nitrogen vacancy centres created by treatment appearing to follow these deformation lines."
The report concludes: "This is a notable example of treatments used to enhance the colour of a natural diamond."
The GIA also recently examined a pair of earrings that were found to contain two assembled pearls, with each base showing distinct layers of materials.
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