5 Minutes
Rare discovery and immediate context
A colossal 2,488-carat rough diamond, nicknamed Motswedi, is under detailed analysis in Antwerp after its discovery last year at the Karowe mine in northeastern Botswana. The stone—roughly half a kilogram in mass—was recovered at Karowe, the operation owned by Canadian miner Lucara Diamond, which has a commercial partnership with HB Antwerp for the processing and marketing of large stones.
HB Antwerp has transported the rough to its Antwerp hub, a global diamond-processing centre, where gemologists are using advanced mapping and scanning tools to assess internal structure, inclusion patterns and the best strategy to convert the rough into polished gems. Margaux Donckier, HB Antwerp's public affairs director, told AFP that a precise market price is premature: "At the moment it's very hard to put a price on it. We first have to inspect the stone and see what we can yield from it in polished form." Donckier said the stone is one of four exceptional discoveries from Karowe, including what is now the world’s third-largest rough diamond.
Valuation challenges, market options and potential buyers
Determining value for an extraordinary rough diamond requires both scientific analysis and market judgement. Key determinants include clarity (internal and surface defects), potential yield after cutting (how much high-value polished carat weight can be produced), color grade, and the rarity premium paid for exceptionally large single stones. HB Antwerp estimates that, collectively, the four significant stones from the recent finds could command at least $100 million, though individual pricing will follow detailed cutting plans and simulated yield scenarios.
High interest is already reported internationally. Donckier noted that buyers range from private collectors and sovereign wealth purchasers to cultural institutions: "The size of these stones is so exceptionally rare that they also perfectly could end up in a museum," she said, while allowing that wealthy private collectors or royal collections could pay a premium. Historical context highlights the rarity: before Motswedi, Botswana’s largest recorded find was the 1,758-carat Sewelo, recovered at Karowe in 2019. The single largest gem-quality diamond known remains the Cullinan (3,106 carats), found in South Africa in 1905; pieces cut from the Cullinan include the Star of Africa in the British crown jewels.
Scientific and gemological background
Diamonds form deep in Earth’s mantle under high pressure and temperature over hundreds of millions to billions of years and are transported to the surface by volcanic kimberlite eruptions. Finding gem-quality stones that exceed thousands of carats is astronomically rare because large, inclusion-free crystal growth requires exceptionally stable conditions. Gemologists now use 3D X-ray tomography, infrared and optical mapping and computer-aided planning to model the optimal way to slice and polish a rough diamond to maximize clarity, color and carat retention while minimizing the risk of fracture.
Cutting decisions balance science and market strategy: sometimes a singular, very large polished stone can fetch greater prestige and price; in other cases, splitting the rough into several high-quality stones yields higher total value.
Expert Insight
Dr. Amelia Hart, Senior Gemologist at the Institute of Gem Science (fictional), commented: "With stones at this scale, the initial non-destructive imaging is critical. Modern tomography gives us a map of inclusions and stress lines, which informs whether to preserve one monumental gem or produce multiple top-grade stones. The historical and cultural value of an intact specimen can rival its market auction value if it enters a museum collection."
Conclusion
Motswedi’s journey from Karowe to Antwerp marks the start of a meticulous scientific and commercial evaluation. While its final fate—museum exhibit, royal collection or a set of world-class polished gems—remains undecided, the discovery underlines Botswana's prominence in global diamond production and highlights how modern gemological science and market strategy together determine the fate and value of extraordinary mineral finds.
Source: sciencealert
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