Petra Diamonds (LSE:PDL) announced it recovered a 25.5 carat blue diamond at the Cullinan mine in South Africa.

The gem is considered to be a of high quality and top colour. Blue diamonds are rare and the most highly coveted.

Previously, the company extracted a similar 26.6 carat rough stone which was polished into a flawless fancy vivid blue 7 carat diamond, which sold at auction for $9.49 million in 2009 and then named the Star of Josephine.

Petra Diamonds has interests in eight producing mines: seven in South Africa and one in Tanzania. The Cullinan mine has produced many of the world's largest diamonds.