A recent study at GIA's New York laboratory delved into the intricacies of a 1.10 carat Fancy Deep brownish orangy pink round diamond, revealing a sophisticated multi-treatment regimen aimed at achieving its distinctive pink coloration. This diamond, subjected to high-pressure, high-temperature (HPHT) annealing, irradiation, and subsequent moderate heating, presented an unusual mottled appearance, sparking further investigation into its unique characteristics. The comprehensive analysis, employing advanced spectroscopic techniques, unveiled the complex interplay of treatment processes and internal structural features contributing to the diamond's aesthetic and scientific intrigue.

The research highlighted the diamond's classification as a type IaAB, characterized by an uneven distribution of nitrogen aggregates, which is believed to be the root cause of its peculiar color distribution. The presence of nitrogen vacancy (NV) centers, a direct result of the multi-treatment, was confirmed as the primary factor responsible for the diamond's pink hue. This case underscores the evolving sophistication in diamond treatment technologies and the continuous need for advanced gemological testing to accurately identify and understand these complex alterations.

The Enigmatic Mottled Coloration of a Multi-Treated Pink Diamond

A 1.10-carat Fancy Deep brownish orangy pink round diamond recently submitted to GIA's New York laboratory showcased an intriguing mottled appearance, a direct consequence of its elaborate multi-treatment. This complex process involved high-pressure, high-temperature (HPHT) annealing, irradiation, and subsequent moderate heating, all orchestrated to induce nitrogen vacancy (NV) centers, thereby achieving the desired pink coloration. The uneven distribution of this pink hue, extending from just beneath the surface to the polished exterior, presented a highly unusual characteristic for a treated pink diamond, distinguishing it from typically uniformly colored counterparts.

The diamond's unique mottled pattern prompted a thorough investigation, revealing a fascinating story of gemological artistry and scientific manipulation. Its initial state, presumed to be an undesirable brownish color, underwent transformation through a precise combination of treatments. The resulting unevenness in color distribution is particularly noteworthy, as it suggests a nuanced response of the diamond's internal structure to the treatment protocols. This case exemplifies the sophisticated challenges and artistic possibilities inherent in modern diamond enhancement, pushing the boundaries of color modification while simultaneously presenting new diagnostic puzzles for gemologists.

Unraveling the Scientific Underpinnings of Color Treatment and Distribution

Spectroscopic analysis provided critical insights into the diamond's internal structure and the effects of its multi-treatment. Mid-infrared spectroscopy classified the diamond as a type IaAB, characterized by A and B aggregated nitrogen distributed throughout its crystal lattice, alongside isolated single nitrogen impurities likely resulting from the HPHT annealing. This uneven distribution of nitrogen aggregates is hypothesized to be directly responsible for the variable NV center distribution, which in turn explains the diamond's subtle and mottled color presentation. The visible/near-infrared (Vis-NIR) absorption spectrum further corroborated the treatment history, displaying peaks indicative of laboratory irradiation and heat treatments, including the 594 nm peak for irradiation, and the NV⁰ and NV^– centers crucial for the pink color, alongside H2 centers signifying heat exposure.

Deep-UV fluorescence images, captured with a DiamondView instrument, revealed a captivating interplay of yellow and orange fluorescence. Both colors are attributable to NV centers, with their specific hue varying based on the ratio of negative to neutral NV center intensities. This variation in NV center distribution and their ratio is intimately linked to the nitrogen aggregate distribution within the diamond, providing a plausible explanation for the observed mottled color. While comprehensive IR mapping for nitrogen aggregate distribution and photoluminescence mapping of NV centers were not performed, the existing data strongly suggests a correlation between these internal characteristics and the diamond's unique visual properties, offering a profound understanding of how complex treatments intricately modify a diamond's appearance.