World’s second-largest diamond awaits a home after appraisal sets its price

A 2,492-carat diamond unearthed in Botswana last year is preparing to enter the market, but its ultimate destination remains uncertain as gem traders await a formal appraisal and a determination of how much of the stone can be polished for sale. The rough gem, known as Motswedi, was discovered at the Karowe mine by Canadian miner Lucara and is widely described as the world’s second-largest gem-quality diamond found in modern times. Its size places it just behind the historic Cullinan Diamond, a 3,106-carat stone discovered in 1905 that was cut into several gems and now forms part of the British crown jewels. The Motswedi has drawn interest from across the globe, but pricing has proved elusive because the stone must be examined to determine how much of it can be yielded in polished form and how its color and clarity may translate into value.

The sourcing and potential sale of Motswedi are unfolding as the diamond trade grapples with rapid changes in the market for ultra‑large stones. HB Antwerp, a boutique dealer known for handling exceptional gems, has presented the Motswedi to potential buyers and is negotiating terms with financiers and collectors. Margaux Donckier, HB Antwerp’s public affairs director, told AFP that pricing is currently the main hurdle; dealers must first inspect the stone to assess the polished yield and the resulting price range. “At the moment it’s very hard to put a price on it,” she said. “We first have to inspect the stone and see what we can yield from it in polished form.”

Image: The Motswedi diamond resting in a hand, illustrating its extraordinary scale.

The rough gem’s discovery adds to a recent wave of interest in extremely large stones from the Karowe mine, located roughly 300 miles north of Gaborone. The mine has yielded several other giants in recent years, including the 1,758-carat Sewelo and the 1,109-carat Lesedi La Rona. In 2017, the Lesedi La Rona set a record when British diamond magnate Laurence Graff purchased it for around $53 million, a price that underscored the premium commanded by stones of such size and potential beauty. Louis Vuitton also acquired the Sewelo Diamond in 2019, though the exact price was not disclosed. These transactions highlight how a single enormous stone can alter the trajectory of a dealer’s portfolio and influence the market for other rare gems.

The Motswedi’s size and expected blue‑white color, combined with its high clarity and rarity, have prompted speculation about possible destinations. Some observers suggest that legendary or museum collections could be drawn to a stone with this historic scale, while others note that private collectors—potentially from the Middle East or other regions with a tradition of collecting significant gemstones—might bid for a centerpiece piece worthy of display. Donckier indicated that while the immediate emphasis is on valuation, the long‑term outcome remains flexible and will depend on how the market responds to the examination results and any potential polishing that could unlock additional value.

Beyond the immediate question of what price the Motswedi could command lies a broader trend in the diamond world. The Karowe mine’s output has drawn comparisons to the era when large, flawless or near‑flawless stones could redefine a dealer’s standing and a region’s reputation within the industry. The market has shown resilience for rare, unusually large gems, even as demand for more common stones shifts in the face of lab‑grown alternatives and evolving consumer preferences. The four‑stone exhibition that HB Antwerp has mounted around Motswedi includes other sizable gems from the same mine, illustrating how a single geologic event can yield a small cluster of extraordinary pieces that attract global attention. Those four stones, according to the dealer, could collectively fetch at least $100 million, a sum that would make the display and sale of this group a watershed moment for the firm and for Botswana’s mining story.

The science behind diamonds adds another layer to the equation. In parallel to natural gemstone production, researchers and entrepreneurs are growing diamonds in laboratories. The emergence of lab‑grown diamonds has unsettled some traditional markets by offering stones with similar chemical and physical properties produced in a matter of hours instead of millennia. These lab‑grown gems are created by placing a seed diamond in a vacuum chamber and introducing hydrogen and methane gas at temperatures around 3,000°C (5,400°F). The resulting plasma drives carbon atoms to arrange themselves in the diamond’s crystal lattice, with growth rates that can be exceedingly fast compared with natural formation. In some lab demonstrations, diamonds have been produced in roughly 150 minutes, underscoring a potential shift in supply dynamics that cutters and retailers are watching closely. The field’s most visible players have published demonstrations and marketing campaigns to show how lab diamonds can offer a cruelty‑free, potentially lower‑cost alternative to mined stones, though natural stones of exceptional size and rarity continue to command premium prices in the high end of the market.

Despite the rise of lab production, the Motswedi remains a potent symbol of natural geology—the result of centuries of pressure and temperature deep beneath the Earth’s crust. Its eventual destination could reflect a confluence of market forces, collector interest, and the evolving relationship between natural and lab‑grown diamonds. For now, the price remains undetermined as HB Antwerp and potential buyers await an official appraisal that will quantify how much of the stone can be cut and polished, and what those polished yields might fetch on the open market. The world will watch to see whether Motswedi ultimately joins the ranks of Cullinan and Lesedi La Rona as a historic stone kept in a public collection, or if it becomes a crown jewel for a private collection or a museum that champions Botswana’s mining story and the science of gemology. The immediate next step is a precise valuation and a polishing assessment, followed by a bidding process that could set a new benchmark for the price of the world’s most enormous rough diamonds. The story of Motswedi is not just about a single stone; it reflects the ongoing transformation of how society discovers, values, and shares its most remarkable natural resources.