Petra finds rare blue diamond

London - Miner Petra Diamonds said it recovered a high-quality 25.5-carat blue diamond at its Cullinan mine in South Africa, sending its shares up as much as 5%.

Blue diamonds are extremely rare and Petra's Cullinan mine has produced some that have fetched hefty prices, including a 26.6-carat rough stone that yielded an internally flawless 7-carat polished stone and sold for $9.49m in May 2009.

"If this is anything to go by, a similar number may be expected to go straight to the bottom line," Numis Securities' Cailey Barker said.

Last November, a flawless deep-blue diamond from Cullinan, which weighed 10.48 carats and was about the size of an almond, was auctioned for 10.27 million Swiss francs and set a world record for a blue diamond per carat.

Petra's shares were up 1% at 108.3 pence at 08:09 GMT on Wednesday on the London Stock Exchange.