Reuters reports that the stone, found in the Letseng mine in Lesotho, is the fifth-largest gem-quality diamond ever found, and the largest in Lesotho’s history. It weighs more than a regulation baseball (about 5 ounces), and more than half as much as the average male human heart (about 10 ounces).
It said the stone is a D color, Type IIa diamond, meaning it is colorless and very radiant, without any yellow tint or impurities like nitrogen that absorb light and decrease luster. Gem Diamond’s stock jumped sharply on news of the discovery, shooting up about 16 percent from 84 pence to 93.20 pence (GBX12.60) within hours of the announcement.
How much the rough stone will fetch at auction remains to be seen, and it will depend in part on any imperfections that limit the size of the cut and polished stones it can be fashioned into. The previous largest find in Lesotho, the 603-carat Lesotho Promise diamond, sold for $12.4 million in 2006, and diamond prices have increased significantly since then.
The largest gem-quality diamond ever discovered, the Cullinan Diamond, weighed more than 3,100 carats, nearly three times as much as the next-biggest. Several of the world’s largest finished diamonds were cut from it and incorporated into Britain’s Crown Jewels.
The Letseng mine, at an elevation of almost 10,000 feet, is known for producing very large, high-quality diamonds. The government of Lesotho, a constitutional monarchy surrounded by South Africa, owns a minority stake in the mine.
Diamonds and garments make up almost the entire export economy of Lesotho, a country with high rates of poverty and HIV infection. It ranks 160th out of 188 countries on the United Nations’ Human Development Index.