$10.4 million worth for one of the Huge Rough Diamond

Sold at $10.4 million, one of the largest rough diamonds is expected to be transformed into a polished stone of more than 100 carats. The huge 493-carat rough diamond from Lesotho, the 18th largest ever recovered in the world, was sold to Graff Jewelers of London at a tender in Antwerp.

Miner Gem Diamonds explained that the diamond recovered at Letseng le Terai mine in September, was sold for an expensive price of $21,000 per carat, against a global average diamond price of $81 per carat. The largest rough quality-gem diamond ever found was the Cullinan Diamond, found in South Africa in 1905, at 3,106.75 carats. "The Letseng Legacy was named to reflect the growing legacy that the Letseng le Terai mine is creating as a producer of significant diamonds," Gem Diamonds said in a statement.

Letseng Diamonds, 70 percent owned by Gem Diamonds and 30 percent owned by the government of Lesotho, has now produced three of the world's top 20 diamonds, including the 603-carat Lesotho Promise. Graff Jewelers were also the winning bidder for the Lesotho Promise in 2006. A brilliant-cut white diamond, which weighs 84.37 carats, was sold at an auction in Geneva on Wednesday for nearly 18.2 million Swiss francs ($16.21 million) to Guess Jeans founder Georges Marciano, Sotheby's said. That diamond was the second most expensive stone ever sold at auction, eclipsed only by the 100.10 carat "Star of the Season" diamond, which went for $16.5 million in May 1995.