Top colour stone found at Cullinan mine in South Africa.

Petra Diamonds has reported the discovery of a 25.5ct blue diamond at its Cullinan mine in South Africa, said to be of high quality and of top colour.

A statement from Petra said: "Blue diamonds are among the rarest and most highly coveted of all diamonds and the Cullinan mine is the most important source of blues in the world.


"Since Petra acquired the mine, it has produced a number of blue diamonds, including a 26.6ct rough stone which yielded a fancy vivid blue and internally flawless 7ct polished stone."

A spokesperson for Petra said the company will reveal its plans for the stone once they are finalised, adding that Petra has had great success selling special diamonds as both rough and polished stones, with the aim always being to maximise value.

The 7ct stone – today known as The Star of Josephine – was sold at Sotheby’s in 2009, for US$9.49 million (£6.22m today) which at the time was the highest price per carat for any gemstone sold at auction and the highest price for a fancy vivid blue diamond sold at auction.

The announcement from Petra comes after yesterday’s new that the 35ct Princie pink diamond sold at auction for £25.5m, making it the most valuable diamond ever sold at auction in the US.