Cullinan is one of the world's most celebrated diamond mines and is a source of large, high-quality Type II gem diamonds. It earned its place in history with the discovery of the Cullinan diamond in 1905, the largest rough gem diamond ever found at 3,106 carats, and it has produced over 750 stones of greater than 100 carats and more than a quarter of all the world's diamonds of greater than 400 carats. It is also the world's only significant source of truly rare and highly valuable blue diamonds.
Since taking over the mine in July 2008, Petra has recovered several world-class diamonds, including a 39 carat blue diamond which sold for US$8.8 million, a 26 carat blue diamond which Petra cut into a 7 carat polished stone and sold for US$9.4 million, and a 507 carat white diamond which Petra named the Cullinan Heritage and sold for US$35.3 million, being the highest price on record for a rough diamond.
Cullinan contains a world-class resource of 202.1 Mcts (including 16.5 Mcts in tailings). Petra is currently implementing an expansion plan at Cullinan which will take production from ~870,000 carats in FY 2012 to 2.4 million carats by FY 2019.
The Cullinan kimberlite pipe was discovered in 1902 and open pit mining commenced at the ‘Premier’ mine (as it was then known) in 1903. Since this time it has produced in excess of 350 Mt of ore yielding approximately 120 Mcts of diamonds. More than 75 Mt of coarse tailings material has been reprocessed and yielded 20 Mcts of diamonds. Ore extraction has been by underground mining methods since 1946. Ore extraction has varied between 2 and 5 Mt per annum and ore treatment between 2 and 7 Mt per annum.
The mine was renamed ‘Cullinan’ as part of its centenary celebrations and to link the mine to the illustrious heritage of the Cullinan diamond, which provided the two main polished diamonds within the British Crown Jewels (the 530 carat Great Star of Africa and the 317 carat Lesser Star of Africa).
Petra initially acquired a 37% interest in the Cullinan mine from De Beers in 2008, but increased its direct interest in the mine to 74% in late 2009 when it acquired Al Rajhi’s holding in the mine. Petra continues to exploit the underground resource using block cave mining methods.