The world's largest diamond sells for £6.6 million 9th October 2006 Lesotho Promise: The huge diamond sold at auction went for £6.6 million A diamond bigger than a golf ball has sold for £6.6 million. The 603-carat gem, named Lesotho Promise after the tiny African kingdom where it was found, is the 15th largest diamond ever to have been unearthed. Safdico, the manufacturing arm of the famous British jewellers Graff, bought it yesterday after beating 13 rival companies in a sealed bid. For the next three months the stone will be minutely analysed in the companys Antwerp factory. Polishing will take a further three months. But incredibly, most of the stone will become dust once it is cut. Yves Alexis, a spokesman for Safdico, said: We are looking at no more than 25 to 30 per cent recovery from a stone like this. "If you achieved this you'd be happy. The rest will just be a pile of dust once weve finished." Not only is the 121-gram diamond large but it is grade D, the highest quality, and is the 10th largest white diamond ever to have been found. Mr Alexis said: "The hefty price is not just because of the size but because of the exceptional quality and colour. It is perfectly white. "To maximise the yield we will spend many months analysing it. It is like a very difficult puzzle we need to crack. You have to navigate your way through the cracks and faults." The Lesotho Promise is a third bigger than a golf ball. Five large diamonds, including a large heart-shaped gem of about 60 carats, and five smaller ones will be cut and ready for sale within a year. The stones are predicted to fetch an estimated £10.7 million. The discovery was made by Agnes Phatela, a 30-year-old employee of Gem Diamond Mining Company of Africa at Letseng Diamond Mine in Lesotho, southern Africa, the highest mine in the world at 3000m. Ms Phatela, who earns about £274.30-a-month (4000 Loti), had just started her shift at 7am on August 22 when she let out a huge shriek. Concerned colleagues ran to her work station fearing she had been electrocuted. Bridget Fury, a spokeswoman for the mine, said: "About 250,000 tonnes of kimberlite rock is processed every two hours in the mine. One carat of diamond can be expected from this. So you can imagine the shock when this 603 carat diamond appeared. "Agnes was working in the processing factory the point when any diamonds that have been separated from the kimberlite shoot down a chute and into a glass container. She suddenly saw this huge rock thump down. She couldnt believe her eyes. She screamed out. Her colleagues thought something was desperately wrong with her and ran over. "They were as surprised and as excited as she was." Employees will not receive a bonus despite the huge sum obtained. Ms Fury said: "Over the months it will all balance out. The mine is not one of the most productive in terms of quantity so the quality has to be relied upon." The mine, which employs 460 people, has been operating for just two years. Fifteen per cent of its diamonds have been bigger than 10-carat. About 80 to 90 per cent of these are D-grade. Worldwide, fewer than one per cent of diamonds are in this category. Twenty companies were invited to view the diamond in Antwerp. Fourteen of these, including Omega Diamonds and Rosy Blue, submitted bids by 10am yesterday. The second highest bid was believed to have been about £700,000 lower than the winning price of £6.63 million ($12.36 million). This sum could buy three-quarters of a tonne of gold. Famously serenaded as a girls best friend by Marilyn Monroe in the 1950s film Gentlemen Prefer Blondes, diamonds have long been a status symbol. Neil Buxton, director of WWW International Diamond Consultants, the firm that marketed the Lesotho Promise, said: "Its been a good day at the office. "This stone is going to make an awful lot of women very happy ladies. "But theyll need to be married to someone very wealthy." The biggest diamond ever to have been found was Cullinan measuring 3106 carats. The second largest was Excelsior at 995 carats. Both were found in South Africa.