Why Sotheby’s Wants Diamond Origin to Matter

Lost beneath the headlines surrounding the exceptional blue diamonds that did and did not sell during Geneva Luxury Week was the continued success of Sotheby’s collaboration with De Beers.

The headline from the Geneva auctions was undoubtedly The Ocean Dream, lot 90 of Christie’s Magnificent Jewels sale on May 13.

After 20 minutes of bidding, the triangular-shape, 5.50-carat, fancy vivid blue-green, SI1-clarity, type Ia diamond sold for CHF 13.6 million ($17.4 million), easily surpassing its pre-sale high estimate of CHF 10 million. It set a new auction record for the color category.

The other notable lot was number 621 at Sotheby’s, a cushion-shape, 6.03-carat, fancy vivid blue, internally flawless diamond that was excluded from the auction house’s results. The diamond did not find a buyer during the auction, though Sotheby’s told The Diamond Press it is “in conversations with several interested parties and is confident that it will find a new home soon.”

Sotheby’s sold 93% of the lots on offer, marking its highest participation rate in five years, while Christie’s sold 99%, both serving as a reminder of the enduring value of natural diamonds and the resilience of the higher end of the market.

Perhaps even more notable, however, was Sotheby’s top lot (number 617) after the headline blue diamond dropped out. That was a pair of unmounted 18.38-carat diamonds, both D-color and graded flawless and internally flawless respectively, which sold for CHF 2.5 million ($3.3 million) to an international private buyer.

The diamonds were cut from rough recovered at De Beers’ Jwaneng mine in Botswana. Their appearance at auction follows the ‘Jwaneng 28.88,’ a round, 28.88-carat, D-color, flawless diamond from the same operation that sold for HKD 21.03 million ($2.7 million) at Sotheby’s Hong Kong High Jewelry sale in April.

It’s important to note that these are not De Beers-owned diamonds. Rather, the Sotheby’s-De Beers collaboration is designed to highlight the provenance of these new-to-market flawless gems at Sotheby’s flagship high jewelry auctions, a De Beers spokesperson explained.

The diamonds are sourced by sightholders and traceable to De Beers origin, with De Beers providing background on the stones. They are not part of the miner’s polished division, as initially presumed by this author. In that sense, Sotheby’s labeling them as De Beers diamonds is somewhat misleading, even if the stones are verifiably tied to De Beers production.

What Sotheby’s and De Beers appear to be testing is whether origin can become part of a diamond’s luxury value proposition. The auctions provide a real-time benchmark for the extent to which origin adds value to the highest-quality stones.

The Jwaneng 28.88 sold for $92,990 per carat, while the 18.38-carat diamonds achieved $89,771 per carat, slightly above the average price in the polished trade. The market for 10-carat and larger diamonds is particularly strong at the moment, with very few stones available, according to one source. “Prices have strengthened significantly and continue to do so,” he added.

It’s therefore not clear whether the origin disclosure really added dollar value to the auction sales, nor whether Sotheby’s expected it to do so. My guess is it did not. What the collaboration does provide, however, is an added layer of assurance that will remain attached to those diamonds moving forward.

That distinction is important, because traceability and provenance are often treated as the same thing in the modern diamond market, when they are not.

The origin disclosure of these diamonds is not, in itself, a provenance play by Sotheby’s. Provenance is built over time, through intrigue surrounding a diamond’s journey, previous famous or infamous owners, or events that add to both the narrative and monetary value of the piece. It’s often why such diamonds or collections are sold at auction, because the auction houses are masters at marketing that intrigue, and stimulating competitive bidding for the buyer to become the next part of the story.

Traceability is different. Knowing a diamond’s origin adds a storytelling dimension that may bring value in the future. In the near term, it serves as a powerful form of authentication that enhances the diamond’s salability. Sotheby’s, with De Beers as its authenticator, is making that a feature of the auction process, and it is slowly becoming an important element of trading in the polished diamond market.

Origin disclosure may not bring a premium for the diamond, but as one diamantaire once told me, it can make a diamond a lot easier to sell.

Image: Quig Bruning, Sotheby's global head of jewelry, auctioning lot 617, the perfectly matched white diamonds sourced with de Beers origin. (Credit: Sotheby's).