True Colours

When the Pink Star Diamond was sold at Sotheby’s in Hong Kong in 2017, most of the people who admired it did not see a lesson in natural history. They saw the world’s most expensive jewel to ever be sold at auction: a scintillating, vivid pink stone cut and polished to perfection, worth US$71.2 million. 

But coloured diamonds, or fancy colour diamonds as they are known in the jewellery trade, are not only smart investments but a map through millions of years’ worth of history. Before the Pink Star was extracted from a South African mine in 1999, it had existed below the surface of the Earth for longer than some of the stars have been in the sky.

Coxon, whose job is to select precious stones for De Beers’ jewellery, explains diamonds are graded according to the four Cs: clarity, cut, carat weight and colour. It is the fourth criterion that can confer serious value: every one of the 10 most expensive diamonds ever auctioned has been a coloured diamond.

Even at more modest ends of the spectrum, coloured diamonds have surged in value over the last decade. Between 2010 and 2019, those who have invested in pink, blue and yellow diamonds have seen an increase in value by an average of 77 percent according to the Fancy Color Research Foundation. 

The Pink Star’s astonishing hue is the result of millions of years of natural processes; a pink or red diamond owes its colour—the rarest of all—to subtle shifts in the alignment of its atomic structure after being subjected to extreme heat and pressure while rising from the depths of the planet.

Coxon has been responsible for determining the quality of every single diamond mounted in a piece of De Beers jewellery for over 20 years, but says he still gets a thrill out of discovering rare new gems. “I got excited about every single one of the diamonds that have gone into our Natural Works of Art collection,” he says, “but I think probably the most exciting one was the 2.78-carat, fancy intense pinkish purple. I could look at it all day and not be bored.”

He keeps only the most extraordinary and rare fancy colour diamonds for the Natural Works of Art collection—one-of-a-kind jewellery pieces designed to showcase these small miracles of nature. His favourite, the fancy intense pinkish purple diamond, is now a solitaire ring, cushion cut and pavé set on a diamond platinum band.

It has been estimated that only one in every 10,000 natural diamonds is classed as a fancy colour diamond, making them exceptionally rare and highly sought-after as investment pieces. Coxon insists that it’s not only colour and rarity that makes them valuable, however.

That’s also, he says, entirely subjective: “Basically, how beautiful is it? Within every colour grade, there can be a 50% difference in price between the most beautiful diamond and those that just matched the colour sample.”

He ultimately advises anyone who’s curious about investment jewellery and fancy coloured diamonds, likening the process to buying art—or finding love. “It’s a bit like choosing your life partner, because often it’s not the one that's recommended. It’s the one you never want to let go.”