Gem Diamonds, a London-listed mining firm, said on Sunday it had recovered a 478 carat diamond from its mine in Lesotho: the 20th-largest rough diamond ever found. The discovery of the gem, which the company said had the potential to become one of the largest round-cut diamonds in the world, was made on September 8 at the Letseng mine in Lesotho. "Preliminary examination of this remarkable diamond indicates that it will yield a record-breaking polished stone of the very best colour and clarity," the company's Chief Executive Clifford Elphick said in a statement. The diamond, which has not yet been named, has the potential to yield a 150 carat polished stone, a company spokesman said. That would be far bigger than the 105 carat round-cut Koh-i-Noor diamond seized by Britain from India in the 19th century and now part of the Crown Jewels. It would still only be a fraction of the size, however, of the Cullinan diamond discovered in 1905, which was 3,106 carats when recovered and yielded a teardrop shaped diamond of 530 carats: the Great Star of Africa. The Letseng mine is owned by a mining company that is 70 percent owned by Gem Diamonds, with the remaining 30 percent held by the Lesotho government. Gem Diamonds's share price on the London Stock Exchange was 741.50 pence at the close of trading on Friday. Source:Yahoo