Flawless white diamonds, among largest ever offered, to go on sale

Two flawless white diamonds each weighing in at more than 50 carats are expected to fetch more than $15 million (10.65 million pounds) when they are auctioned in May, auctioneers Sotheby's Diamonds said on Friday.The diamonds, a 51.71 carat round brilliant-cut gemstone and a 50.39 carat oval, are the second-largest of their respective kinds ever to come to auction, Sotheby's said.The sale of the gemstones, discovered and purchased at tender in Botswana, comes after a 102 carat white diamond sold