Welcome to our second installment of Captivated by Colour and this time, we’re looking at pink diamonds. Pink diamonds are one of the rarest colours of diamonds and one of the most prized and valued. Many people will ask about coloured diamonds, but very few people know how rare they are, or how expensive they are. Diamonds are of course April’s birthstone and are still the most popular gemstone for engagement rings.
What gives pink diamonds their colour?
Whilst many diamond colours are a result of chemical impurities in the diamonds (for example, yellow diamonds are a result of nitrogen impurities), the colour in pink diamonds is a factor of something completely different. A GIA study of over 90,000 red, purple, pink and brown diamonds concluded that distortion in the crystal structure of a diamond gives rise to these fancy colours 99.5% of the time. In pink diamonds, the colour is generally concentrated along parallel narrow bands called lamellae, or glide planes. Interestingly, the atomic level distortions caused by plastic deformation that result in pink diamonds have not been replicated in a laboratory. Roughly translated, plastic deformation is a permanent change in shape of an item because of stress or force being applied to it.
Where do pink diamonds come from?
Pink diamonds have been found in many countries, including South Africa, Botswana, Canada, Tanzania, Russia and Brazil. However, Australia has been the world’s leading supplier of pink diamonds for decades, with approximately 90% of pink diamonds originating from the Argyle Diamond Mine in Western Australia. Not only is the Argyle mine the most prolific supplier of pink diamonds, it differs from all other primary diamond sources in that the host rock for the diamonds is lamproite, as opposed to kimberlite. To give you an idea of how rare pink diamonds are, only approximately 1% of the diamonds found in Argyle are pink. Most are brown in colour, but occasionally red, purple and violet colours are uncovered. These remarkable diamonds are auctioned every year during Argyle’s Pink Diamond Tender.
Tragically, Argyle Diamond Mine is due to close towards the end of 2020 after 35 years of operation, due to reduced economic viability.