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

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.