The Science Behind Pink Diamonds

Introduction

Welcome to GIA Knowledge Sessions, a series of talks about gemology, drawing on decades of research at GIA. In this session, Dr. Sally Magana, the senior manager of Diamond Identification, will discuss the science behind pink diamonds. Pink diamonds are a rare subset of the already rare colored diamond family, and their unique characteristics make them highly valued in the gemstone market.

Understanding the Color Distribution of Pink Diamonds

Pink diamonds come in various shades and intensities, ranging from very light to fancy red. The color distribution can be seen within the pink family, which includes straight pink diamonds, pinkish-purple, brownish-pink, and orange-pink diamonds. These different hues all result from similar causes of color, which will be explained in detail throughout this talk.

The Role of Nitrogen in Pink Diamonds

Nitrogen is a key element in the formation of pink diamonds. Most diamonds start with single and isolated nitrogen atoms, which eventually pair up to form aggregates. The type of nitrogen aggregates present in a diamond determines its color and other characteristics. For example, type Ia diamonds have a mixture of A and B aggregates, while type IIa diamonds have no detectable nitrogen.

The Formation Process of Pink Diamonds

Pink diamonds are formed under specific geologic forces. They are typically exposed to high temperatures and pressures, which cause plastic deformation and create the pink color. The exact process and depth at which pink coloration occurs are still not fully understood, but researchers have observed that pink diamonds from the Argyle Mine in Australia are often associated with eclogitic inclusions formed at around 1200 degrees Celsius.

Golconda Pinks: The Rare Pink Diamonds

Golconda pinks are a subset of pink diamonds that are exceptionally rare. They get their color from nitrogen-vacancy (NV) centers, which are formed through a combination of natural radiation and low-temperature heating. Golconda pinks are characterized by their pale color and unique fluorescence under ultraviolet light, which is directly related to the nitrogen-vacancy centers present in the diamonds.

Color Treatment and Bleaching of Pink Diamonds

Pink diamonds can be treated to enhance their color. The most common treatment involves irradiating diamonds with nitrogen and inducing vacancies to create NV centers. This treatment is used for both natural and lab-grown diamonds. It's worth noting that pink diamonds, including Golconda pinks, can undergo temporary bleaching when exposed to ultraviolet light. However, the color reverts back to its stable state over time.

Conclusion

Pink diamonds are a fascinating subset of the diamond family, known for their rarity and unique characteristics. The science behind their coloration involves nitrogen-vacancy centers, plastic deformation, and specific geological processes. As the Argyle Mine, a major source of pink diamonds, is set to close, the future of pink diamond supply remains uncertain. However, the beauty and allure of pink diamonds continue to captivate gemstone enthusiasts and collectors around the world.

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