In 2021, the De Beers mining giant teamed up with diamond manufacturer Diacore to buy a rare blue diamond that had been unearthed at the famed Cullinan mine in South Africa that year. Together, the two companies bought the 39-carat gem for a total of $40.2 million, making it the most expensive rough diamond ever sold.
Now, a 15-carat diamond cut from that rare stone recovered last year is coming to auction this spring. Sotheby’s is selling the blue diamond during a jewelry sale in Hong Kong in April. When it hits the block, it is expected to fetch $48 million. It will be the largest vivid blue diamond ever to be offered at auction.
“It is extremely rare and unique,” said Bruce Cleaver, CEO of De Beers Group, whose company spent the last year working with Diacore to perfect the step-cut gem. Sotheby’s is expecting the diamond sale to draw attention from global bidders, given its rarity and size.
“Nothing of remotely similar calibre has appeared at auction in recent years,” said Patti Wong, chairman of Sotheby’s Asia.
In 2015, during a Sotheby’s sale in Geneva, the house set a record for the most expensive blue diamond ever sold at auction when a stone known as the Blue Moon of Josephine went for $48.5 million.
Blue diamonds are among the world’s rarest stones. For many years, experst have been unsure how their color came to be. Geologists now attribute the blue color to the presence of trace amounts of the uncommon element boron in the stones, which often takes hundred of millions of years to form and are often sited deep in the earth.
The diamond is on view at Sotheby’s galleries in New York, and will then travel to exhibition spaces in London, Dubai, Singapore, Shanghai, Beijing, Shenzhen, and Taipei before reaching its final stop in Hong Kong, where it will be sold.