LONDON (AFP) -- A 603-carat white diamond, the 15th largest ever found, has sold for 12.36 million dollars (9.73 million euros), owners of a Lesotho mine where the jewel was discovered have said.

Safdico, the manufacturing arm of Graff Jewelers, won the bidding for the Lesotho Promise at a sale in Antwerp last Wednesday, according to the mine's joint owners, South Africa's Gem Diamond Mining and the Lesotho government.

"We are thrilled to have won the tender for this magnificent and historical jewel," Safdico representative Yves Alexis said in a joint statement.

The diamond had been found at the Letseng Diamond Mine in the tiny mountain kingdom of Lesotho.

It went on sale the day the southern African kingdom marked its 40th anniversary of independence from British rule.

"We are delighted with the price achieved for this historically significant stone," Gem Diamonds chief executive Clifford Elphick said.

The Lesotho Promise is rated D, the top color for diamonds. The largest diamond previously found in Lesotho was the 601-carat Lesotho Brown unearthed in 1967.

Other world-famous diamonds from southern Africa include the 3,106.75-carat Cullinan diamond, which was split in two and forms part of the British crown jewels.