Mining company in South Africa finds rare blue diamond

A rare blue diamond has been unearthed at a mine in South Africa.The 25.5-carat stone was recovered by Petra Diamonds at its Cullinan mine and is expected to bring large profits.Experts say it could be worth more than $10m (£6m), and the find gave a boost to Petra's share price.Similar finds in recent years from the Cullinan mine have commanded high prices and Petra, with operations in Botswana