World’s largest blue diamond, ‘exceptionally rare’ at 15 carats, sells for $57 million.

The world’s largest blue diamond now has a price tag to match its rarity. 

The 15.10-carat diamond, called “The De Beers Cullinan Blue,” sold for $57.5 million Wednesday in an auction at Sotheby’s in Hong Kong.

The one-of-a-kind diamond had been expected to sell for about $48 million, but an anonymous buyer secured the gem via phone after an eight-minute bidding war among four potential buyers. 

A press release from Sotheby’s noted that the diamond comes from South Africa’s Cullinan mine and was obtained in 2021. It has since attained all of the highest rankings on which colored diamonds are assessed. The Gemological Institute of America (GIA) categorized the jewel as “fancy vivid blue” – the top color grading of its class. 

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“Blue diamonds of this importance are exceptionally rare, with only five examples over 10 carats ever having come to auction, none of which have exceeded 15 carats, making the appearance of this flawless gem a landmark event in itself,” a Sotheby’s statement said.

With a final price of $57,471,960, the gem barely missed eclipsing the record for the most expensive blue diamond ever to sell at auction. The 14.62-carat “Oppenheimer Blue” sold in 2016 for $57,541,779. That’s a difference of just under $70,000.

“It is truly a once-in-a-generation stone, and quite simply the greatest blue diamond of its size I have ever seen,” Patti Wong, chairman of Sotheby’s Asia, said in a statement.