A seven-carat blue diamond discovered at the Cullinan diamond mine near Pretoria has been sold in Geneva for a record price of nearly U.S. $9.5 million.

The owners of the mine, Petra Diamonds, said in a statement Wednesday that the price fetched at a Sotheby's auction - $1.3 million per carat - set "a new record price per carat for any gemstone sold at auction and the highest price for a fancy vivid blue diamond sold at auction."

Sotheby's said the diamond had drawn particular interest from Hong Kong, New York, London and Geneva.

The stone is, in diamond traders' terminology, an internally-flawless "fancy vivid blue" weighing 7.03 carats. It was cut from a 26.58-carat rough stone found last year.

In a deal first announced in 2007, a consortium led by London-based Petra Diamonds bought the Cullinan mine from De Beers Consolidated Mines. The consortium included a South African black empowerment partner company, Thembinkosi Mining Investments (Pty) Ltd.

The mine has long been renowned for the quality of its diamonds, the most famous of which is the Cullinan diamond, which was discovered in 1905 and at 3,106 carats is still the largest gem diamond ever found. Two diamonds cut from the rough stone, the Great Star of Africa and the Lesser Star of Africa, are in the British crown jewels.