People have been mining for diamonds for more than 2,000 years. The sparkling stones have always been rare, and while size isn’t necessarily a determinant of quality, large diamonds have always held a particular fascination. Modern technology has helped recover some of the largest diamonds ever, which is probably why seven of the 15 stones on our list were discovered in the 21st century. (Diamonds, of course, are one of the most expensive materials on Earth.)

To compile a list of the15 biggest diamonds ever discovered, 24/7 Tempo consulted the websites of the Cape Town Diamond Museum, Geology.Com, and several high-end jewelry retailers. Diamonds are ranked by their pre-cut weight in carats. Both gem-quality and non-gem-quality diamonds are included. Many of these diamonds were later cut into some of the largest gems on Earth. Several of the more recent diamonds discovered are unnamed. 

The “black diamond” called the Carbonado do Sergio, discovered in 1895 in Brazil’s Bahia State, is sometimes named as the world’s biggest diamond (it weighed in at 3,167 carats, or 22.3 ounces), but according to the International Gem Society, it isn’t really a diamond, but is “more accurately described as a polycrystalline or aggregate diamond material of amorphous carbon, graphite, and diamond” – so it is not included here.

All but one of the stones on this list were found in Africa, and specifically in the countries of Botswana (six), South Africa (three), Sierra Leone (two), the Democratic Republic of Congo (two), and Lesotho (one). A single Botswana location, the Karowe Mine, has yielded five of that country’s six. The single outlier, the fabled Kooh-i-Noor Diamond, was found in the 13th century in India – the first place on earth where diamonds were mined. (See which African nations are among the countries with the worst wealth inequality.)

The Canadian-based Lucara Diamond Corp. operates the Karowe Mine, and an important factor in its success at locating large stones is its use of X-Ray transmission (XRT), which Lucara began utilizing in 2015. This has enabled Lucara to recover 33 stones more than 100 carats. The technology measures the ore’s atomic density to identify diamonds at earlier stages, allowing recoveries of larger stones. 

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While African countries have long been the most prolific source of diamonds, mining there is burdened with racial baggage because indigenous peoples were exploited and worked to extremes in colonial times. A concern today is the sale of so-called blood (or conflict) diamonds, mined in war zones and sold to support rebel groups or terrorists. Various international attempts to stem the flow of such diamonds into the marketplace have met with mixed results.