Petra Diamonds unearthed a 122.5 carat blue diamond at its Cullinan mine, the site of the discovery of the world’s largest gem 109 years ago, the group said on Friday. The stone would not be sold before its current financial year ended on June 30. “The stone will require further analysis to assess its potential value,” the group said. When the assessment had been done, “Petra will be in a position to evaluate its optimal route to market”. The Cullinan mine is renowned for producing large blue diamonds, which sell for a premium. The world’s biggest certified diamond is the 3 106 carat Cullinan, found at the mine near Pretoria in 1905. It was cut to form the Great Star of Africa and the Lesser Star of Africa, set in the Crown Jewels of Britain. – Bloomberg