'Extremely rare' pink diamond expected to sell for more than $21m goes on display in Dubai

The Williamson Pink Star will be auctioned by Sotheby's in October

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Sotheby’s Dubai unveiled a rare, fancy vivid pink diamond on Monday, expected to sell for more than $21 million when it goes to auction next month.

Called the Williamson Pink Star, it weighs an impressive 11.15 carats, and has been certified as “internally flawless” and “fancy vivid” — the highest grade of coloured diamond available. It is only the second pink diamond of this calibre and weight to ever come to auction.

$21 million diamond in Dubai

$21 million diamond in Dubai

Revealed at a ceremony at the Dubai Diamond Exchange, it will go on public display from Tuesday at the Monogram Room, Four Seasons Hotel Dubai International Financial Centre, before travelling to Singapore and Taipei ahead of the auction on October 5.

Wenhao Yu, chairman of jewellery and watches at Sotheby’s Asia said: “The discovery of a gem-quality pink diamond of any size is an extremely rare occurrence. Driven by a limited supply and rising demand, prices for top-quality large pink diamonds over 5 carats have increased exponentially over the past decade, serendipitously setting the scene for the appearance now of this one-of-a-kind stone.”

Only two fancy vivid pink diamonds are known to be larger than this one, and of those only one has ever appeared at auction. The CTF Pink Star, an oval-shaped fancy vivid pink stone weighing a monumental 59.60 carats, was sold at auction in April 2017 for $71.2 million, setting a world record for the "most expensive diamond, gemstone or jewel", that still stands five years later.

The other stone will never come on to the market, as it was gifted to Queen Elizabeth II as a wedding present in 1947. Weighing 23.60 carats, it was presented by John Thorburn Williamson, the owner of the Tanzanian mine where it was unearthed.

Coloured diamonds are exceptionally rare, and take their hue from trace elements. Blue diamonds, for example, take their colour from boron, while yellow gems contain nitrogen. Pink diamonds, however, are different, as no found trace elements have ever been identified. Instead, the unique colour is thought to be created by distortions in the diamond's crystal lattice, caused by immense heat and pressure.

To this end, coloured diamonds are highly sought after by dealers and collectors alike, because of all the stones sent to the Gemological Institute of America or GIA for verification and grading, less than 3 per cent are deemed to be coloured diamonds. Of those, less than 5 per cent are classified as being pink, making it the rarest diamond of all.

Updated: September 05, 2022, 3:33 PM