De Beers and Sotheby’s Unveil 28.88 Ct. Diamond Ahead of Auction

By Annie Davidson Watson | March 23, 2026

De Beers and Sotheby’s unveiled the Jwaneng 28.88 at a store in London last week, setting the stage for the internally flawless diamond’s appearance in the April 23 High Jewelry sale in Hong Kong, where it’s estimated to fetch up to $2.8 million.

Sotheby’s has placed an estimate of 17 million to 22 million Hong Kong dollars—around U.S.$2.2 million to $2.8 million—on the 28.88 ct. round brilliant diamond, which is classified as Type IIa. Fewer than 2% of all natural diamonds are classified Type IIa, denoting the highest level of chemical purity.

The D-color stone was cut from a substantial 114.83 ct. rough stone discovered at Botswana’s Jwaneng mine, owned by Debswana, a joint venture between De Beers and the government of Botswana. Other De Beers diamonds will also be offered in Sotheby’s sale, one of the auction house’s Luxury Week events in Hong Kong.

The Jwaneng diamond

“The Jwaneng 28.88 is a perfect emblem of De Beers’ unmatched legacy in diamonds,” said Quig Bruning, head of jewels at Sotheby’s, said in a statement. “It’s at once a vanishingly rare feat of nature, combined with a master class in diamond cutting and polishing. Natural diamonds truly are forever, and I cannot think of a better stone to symbolize this special collaboration.”

The London unveiling, held at Maison Assouline bookstore, coincided with the release of A Diamond Is Forever: The Making of a Cultural Icon, 1926–2026 by art book publisher Assouline. De Beers said it is marking 100 years of jewelry history in 2026 and the 80th anniversary of its iconic “A diamond is forever” slogan in 2027.

The Assouline event featured an exhibition, curated by Sophie Oppenheimer, that traced the dialogue between diamonds and art through archival advertising and seminal works. Celebrities in attendance included actress Nathalie Emmanuel (Game of Thrones) and model Poppy Delevingne.

(Photos courtesy of Sotheby’s)

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