Gem Diamond shares rise sharply after 910-carat find

A 910-carat, D color Type IIa diamond from the Letseng mine in Lesotho.
Gem Diamonds
A 910-carat, D color Type IIa diamond from the Letseng mine in Lesotho.

The share price of U.K.-listed Gem Diamonds has risen sharply after the miner said it had unearthed what is thought to be the fifth largest gem-quality diamond ever found.

The 910-carat rock was extracted from the firm's Letseng mine in Lesotho and, according to analysts at Liberum, could sell for as much as $40 million.

Liberum said it had "large caveats" on its estimate but still raised the analyst rating on the stock to buy from hold. By midday Monday, the share price of Gem Diamond had risen more than 15 percent.

Clifford Elphick, Gem Diamonds' chief executive officer, said in a press release Monday that the discovery was a "landmark recovery for all of Gem Diamonds' stakeholders."

The largest gem-quality rough diamond ever discovered is the 3106-carat Cullinan diamond that was discovered in South Africa's Premier Mine in 1905. It was cut into 105 diamonds including the 530-carat Great Star of Africa.

The largest cut diamond in the world is the Golden Jubilee Diamond, which weighs 545.67 carats. It was also hewn from a rough diamond found in the Premier Mine in 1985.