Stunning 1094-carat diamond named 'Seriti' receives an initial $12 million valuation

Lucara Diamond Corp. reports that a 1,094-carat rough diamond, named Seriti, delivered an initial $12 million in revenue through its specialized sales channel, with an additional percentage of the polished stone profits set to come in the future.

This resulted in a strong lift for the company’s second quarter results at the Karowe mine in Botswana.

In July 2025, the same operation recovered a 2,036-carat rough, a size that places it among the largest documented finds and confirms Karowe’s unusual talent for super-sized stones.

Lucara’s “special” diamonds

Very large diamonds are rare at most mines, but Karowe produces them consistently. In the trade, stones of 10.8 carats and larger are called “Specials,” diamonds above the 10.8-carat threshold, and that category drives much of Karowe’s value.

A single rough of 1,094 carats weighs about 7.7 ounces, which is hefty for a gem crystal. That weight helps explain why a single sale can change a quarterly revenue picture.

The work here is led by William Lamb the President and Chief Executive Officer at Lucara Diamond Corp. Lucara operates the Karowe Mine in Botswana.

Miners gauge output quality with carats per hundred tons of ore (CPHT), a simple rate that tracks how many carats come from a fixed amount of rock. A higher value points to richer or more favorable zones in the orebody.

How the sale works

Lucara channels its largest stones through a long term arrangement with HB Antwerp that prices rough using an estimated polished value and then trues up after the polished diamonds are sold. The approach ties miner revenue to finished market outcomes rather than a one day auction result.

That model includes “top up” or “top down” adjustments once actual polished sales clear, which adds some short term variability but aims to capture more of a stone’s final value. It also pushes the company to plan around polished market signals rather than only rough demand.

“The Karowe Diamond Mine continues to validate its world class status with the recovery of a second diamond exceeding 2,000 carats,” said William Lamb, who’s the President and Chief Executive Officer at Lucara Diamond Corp.

For a stone like Seriti, this route matters because the biggest roughs often yield several polished gems of different qualities. A pricing mechanism linked to polished value helps align incentives across the cut and polish stage.

Big stones from Karowe

Karowe sits on a body of kimberlite, a volcanic rock that carried diamonds from deep mantle levels to the surface, and its different lobes have distinct diamond size distributions, as detailed in the mine’s technical report. One unit, labeled EM/PK(S), is known for frequent large stone recoveries.

Engineers now use advanced sorting, including X ray transmission systems, to spot and protect large crystals before they could crack in crushers. That reduces breakage and preserves size, which protects value and keeps giant roughs intact.

Karowe also yields many Type IIa, diamonds with no measurable nitrogen or boron impurities, which are chemically very pure and often colorless, a trait that can lift polished value according to the GIA.

Type IIa remains a tiny slice of global diamond output, so when mines hit a patch rich in these stones, the market notices.

Geology and careful mining help, but so does planning based on rock behavior. The company has been reviewing geomechanics to refine extraction levels and ensure large stones can be recovered safely as underground work advances.

Market facing two opposing forces

Lab grown diamond prices have fallen sharply, with industry leaders warning that oversupply is undercutting consumer confidence in synthetics.

That price slide puts pressure on mid market natural stones that compete on shape and size rather than rarity.

At the top end, the calculus looks different. Big natural diamonds remain scarce, supply growth is limited, and museum quality or collector grade stones keep drawing attention from buyers who focus on rarity over price per carat.

Lucara also flagged tighter liquidity in its latest filing, noting a technical default on a modeling covenant that led to its project facility being classified as a current liability.

The company said lenders had not demanded early repayment and that it was working on remedies as underground development continued.

A key point for readers is the accounting language itself. Going concern, an accounting assumption that a company can meet its obligations for the next 12 months, becomes a focal measure when a miner shifts from open pit to underground and bridges with lower value stockpiles.

Botswana, Lucara, and diamonds

Botswana remains a powerhouse in diamond value terms, and Karowe sits near the center of that story. Each large recovery adds export value and supports downstream activity, from cutting to retail partnerships.

Tall rough sizes also keep the scientific side interesting. Large crystals preserve clues about deep Earth conditions and mantle chemistry, which GIA labs and academic groups study when stones are submitted for grading or research access.

The story blends earth science, engineering, and markets. Rocks form under heat and pressure, miners plan around rock strength and fracture patterns, and sales models have to match how modern buyers assign value.

It also shows how a single giant stone can change corporate math. When a mine produces a handful of very large diamonds in a quarter, the revenue jump can be dramatic because the value curve rises faster than size alone.

Watch for how Lucara sequences underground production into the EM/PK(S) lobe, where the value per ton can be higher. The timing of that shift will influence cash flow, development spending, and how often we hear about record sized stones.

Also watch polished demand at the high end. If collectors and luxury houses keep favoring rare natural diamonds, large Type IIa goods from Botswana will stay in the spotlight.

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