De Beers Unveils 28.88-Carat Flawless Diamond Ahead of Sotheby's Auction

Few stones enter the auction market with the geological and cultural weight of the Jwaneng 28.88. De Beers, in partnership with Sotheby's, unveiled the 28.88-carat round brilliant diamond at Maison Assouline in London last month, where it made its public debut alongside the launch of A Diamond Is Forever: The Making of a Cultural Icon, 1926-2026, a book marking a century of diamond storytelling. The stone heads to Sotheby's High Jewellery sale in Hong Kong on April 23, where it carries a pre-sale estimate of $2.2 million to $2.8 million.

The diamond's credentials are extraordinary even by the standards of fine jewellery auctions. It is graded D-color and internally flawless, placing it at the apex of both the GIA color and clarity scales. More significantly, it is a Type IIa stone, a gemological classification accounting for fewer than 2% of all natural diamonds and recognized for exceptional chemical and optical purity, with virtually no nitrogen impurities present in the crystal lattice. De Beers' master craftsmen cut the polished stone from a 114.83-carat rough, the result of months of planning and precision work to arrive at the final 28.88-carat form.

That rough was recovered from Botswana's Jwaneng mine, operated by Debswana, a 50/50 joint venture between De Beers and the Government of Botswana. Jwaneng is widely regarded as the world's richest diamond mine by value, a superlative made quietly ironic by the fact that the name translates to "a place of small stones" in Setswana. The mine's history of exceptional recoveries includes a 1,098-carat gem-quality rough unearthed in June 2021, considered one of the three largest gem diamonds ever mined.

The decision to debut the stone in London and sell it in Hong Kong carries deliberate cultural weight. The number 88 holds deep associations with prosperity and fortune in Chinese tradition, and placing the stone before Hong Kong collectors adds a symbolic dimension no gemological certificate can supply. Quig Bruning, head of jewels at Sotheby's, framed the collaboration plainly: "It's at once a vanishingly rare feat of nature, combined with a masterclass in diamond cutting and polishing."

The Jwaneng 28.88 will appear alongside additional diamonds recovered from the same Botswana mine, giving the sale a unified provenance narrative that single-stone lots rarely carry. At a moment when the broader natural diamond market is absorbing pressure from lab-grown alternatives at lower price points, a stone of this classification occupies an entirely separate conversation: one where documented geological origin, Type IIa purity, and the exacting labor of cutting a flawless 28-carat round brilliant from rough represent a combination that cannot be manufactured.