Gem Diamonds said “an exceptional” 196 carat rough white diamond has been recovered from the Letseng mine in Lesotho.

The company said the rough diamond is expected to achieve a substantial price per carat as preliminary examinations indicate that it is expected to produce top colour and top clarity polished diamonds.

Gem Diamonds has found three of the world’s 20 largest diamonds since it acquired the mine in mid 2006, including the 603 carat Lesotho Promise, recovered in August 2006, which was sold for $12.4m.

The company holds a 70% interest in the mine while the rest is owned by the Government of Letseng.