Rough diamond under the hammer for $11.7 million

The huge 493-carat rough diamond from Lesotho in South Africa, the 18th largest ever recovered in the world, was sold to Graff Jewellers of London at a tender in Antwerp on Wednesday.

Miner Gem Diamonds says the diamond, recovered at Letseng le Terai mine in September, sold for an extraordinary price of $US21,000 per carat, against a global average diamond price of $US81 per carat.

The largest rough gem-quality 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 per cent owned by Gem Diamonds and 30 per cent owned by the government of Lesotho, has now produced three of the world's top 20 diamonds, including the 603-carat Lesotho Promise.

Graff Jewellers were also the winning bidder for the Lesotho Promise in 2006. © 2007 Australian Broadcasting Corporation