Fancy Colored Diamonds

The most expensive gemstones sold at auction are not D-colour flawless diamonds. They are fancy coloured diamonds — and specifically, the rarest fancy pinks and fancy blues. The 59.60-carat Pink Star sold for US$71.2 million in 2017. The 14.62-carat Oppenheimer Blue sold for US$57.5 million in 2016. The 11.28-carat Blue Moon of Josephine sold for US$48.5 million in 2015. Understanding fancy coloured diamonds — their causes, their grading, their rarity hierarchy, and their commercial significance — is essential knowledge for any professional serving the upper end of the fine jewellery market.

What Makes Diamond Fancy Colored

Colourless (or near-colourless) diamonds are the result of chemically pure carbon crystallising in the cubic system. Colour in diamond arises from structural defects or impurities that create absorption of specific visible wavelengths. The most common colouring mechanisms are nitrogen (yellow and orange colours), boron (blue), hydrogen (violet), radiation damage (green surface colour), plastic deformation of the crystal lattice (pink and red), and combinations of these.

Yellow and Orange Diamonds

Yellow diamonds are the most common fancy colours, caused by nitrogen atoms substituting for carbon in the lattice. The GIA colour grading system transitions from the colourless-to-near-colourless range (D through Z) to the fancy colour range when yellow or brown intensity increases beyond Z. Intense, vivid yellow diamonds — “Canary” yellows — are extremely attractive and more accessible in price than fancy pinks or blues. Orange diamonds, from a combination of nitrogen and structural defects, are rarer than yellow.

Pink and Red Diamonds

Pink diamonds are among the rarest and most valuable naturally occurring gems. Their colour is caused by plastic deformation of the crystal lattice during the diamond’s journey through the mantle — a process that creates local disruptions in the crystal structure that absorb green light, leaving pink. The Argyle mine in Western Australia, which closed in November 2020, was responsible for approximately 90% of the world’s pink diamond production. Argyle closure has made pink diamonds significantly rarer and prices have increased dramatically since 2020.

Red diamonds are the rarest of all fancy colours — a true vivid red natural diamond has only been documented a handful of times in history. The Moussaieff Red, a 5.11-carat fancy red, is considered one of the rarest gems in existence. Most diamonds described as “red” in the market are actually strong fancy purplish-pink or deep brownish-red.

Blue and Violet Diamonds

Blue diamonds are coloured by boron atoms substituting for carbon, making them semiconductors (most diamonds are insulators). The Hope Diamond, the most famous coloured diamond in the world, is a deep blue Type IIb diamond coloured by boron. Boron-coloured blue diamonds are extraordinarily rare. Many commercial “blue” diamonds are actually irradiation-treated to create colour. Laboratory testing is essential to distinguish natural blue from treated blue diamonds.

Green Diamonds

Natural green diamonds get their colour from radiation damage — the crystal was exposed to natural radiation (from uranium-bearing minerals in the host rock) that displaced carbon atoms and created colour centres. The green colour is typically a surface phenomenon that must be preserved during cutting. The Dresden Green, a 41-carat natural fancy green diamond in the Albertinum museum, is one of the finest natural green diamonds known.

GIA Fancy Color Diamond Grading

GIA grades fancy coloured diamonds on hue, saturation, and tone using descriptors: Faint, Very Light, Light, Fancy Light, Fancy, Fancy Intense, Fancy Vivid, Fancy Deep, and Fancy Dark. “Fancy Vivid” is the highest saturation descriptor and typically commands the highest prices for a given hue, particularly for pink, blue, and yellow. For pink diamonds, Fancy Vivid Pink is the pinnacle of the colour grade scale and the designation that appears on the most valuable pink diamond reports.