Diamonds / Industry

King of the Blues: 15.1 Carat De Beers Cullinan May Set Record


On April 27, Sotheby’s Hong Kong will hold a single-lot auction for the largest and potentially most valuable blue diamond ever to come under the hammer—a 15.1 ct. internally flawless step-cut, called the De Beers Cullinan Blue.

The diamond has a value “in excess of $45 million,” said Sotheby’s. (There’s a reserve, but it’s not public.) The gem has been graded fancy vivid blue and internally flawless by the Gemological Institute of America.

There have been only five blue diamonds over 10 carats ever to appear at auction, and, until now, none of them has topped 15 carats.

“It is one of the most important diamonds we have ever sold at auction,” Wenhao Yu, chairman of jewelry and watches at Sotheby’s Asia, tells JCK. “It is not easy to do a step-cut colored diamond. It is type IIB. It is a one-of-a-kind masterpiece, comparable to an important artwork. It’s a unique piece of nature.”

He doesn’t know if the diamond will fetch a record price, though in the past, aqua diamonds like the Blue Moon have.

“That’s one of the things about auctions, you never know until that night,” he says. “It has the potential to set a record. Not many diamonds can compare to this one.”

An important colored diamond hasn’t come on the market in a while, he says, but he notes the top auction pieces have done extremely well.

“The price for rough has risen by 10%–15% since last year. The market for top artwork, top masterpieces, has been really strong.”

Unlike other recent auctions, the auction house hasn’t announced whether it will accept cryptocurrency.

“We wouldn’t shut the door completely [to crypto],” says Yu. “If there is a serious qualified buyer, we’ll consider it.”

The diamond was named after the mine where it was discovered, the Cullinan, in Gauteng province, South Africa. Yu believes its provenance could add to its value—similar to the way a Kashmir sapphire or a Colombian emerald carries extra cachet—as the Cullinan is considered the world’s only source of important blue diamonds.

“The fact that it was found in the Cullinan has significant importance in Asia,” he says. “We have buildings named after the Cullinan here.”

petra blue diamond de beers
The original piece of rough (photo courtesy of De Beers)

It has also been named after De Beers, though, ironically, it was not found at a mine the company (currently) owns.

It was cut from a 39.34 ct. type IIb blue gemstone, discovered in April 2021 at the 119-year-old Cullinan, which is owned by Petra Diamonds. De Beers was its original owner but sold the mine to Petra in 2007.

The auction may be an interesting test of De Beers’ savvy in dealing polished. When the rough went up for sale five months later, De Beers and 50-50 partner Diacore bought it for $40.2 million. That was the highest price Petra had ever received for a single stone.

De Beers Cullinan Blue_Estimated in Excess of US$48 Million (ii)
Another shot of the Cullinan Blue (photo courtesy of Sotheby’s)

The decision to add De Beers’ name to the diamond seems part of the company’s continued attempt to raise its profile and brand name.

Spokesperson David Johnson tells JCK: “The polished outcome is so rare and exceptional we are proud for it to carry our name.”

Before De Beers and Diacore bought that piece of rough, in November 2020, they spent $40.3 million of a parcel of five rough blue stones, also from the Cullinan. There’s been no word on their plans for those gems.

The diamond was displayed at Sotheby’s gallery in New York City on Tuesday. After that, it will travel to London; Dubai, United Arab Emirates; Singapore; Taipei, Taiwan; and Shanghai, Beijing, and Shenzhen, China.

Top: The De Beers Cullinan Blue (photo courtesy of Sotheby’s)

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By: Rob Bates

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