Cullinan Diamond
The Cullinan diamond was found below the surface at Premier Mine in Cullinan, Transvaal Colony, by Frederick Wells, surface manager at the mine, on 26 January 1905. It was approximately long, wide, deep, and weighed . Newspapers called it the "Cullinan Diamond", a reference to Sir Thomas Cullinan, who opened the mine in 1902. It was three times the size of the Excelsior Diamond, found in 1893 at Jagersfontein Mine, weighing . Four of its eight surfaces were smooth, indicating that it once had been part of a much larger stone broken up by natural forces. It had a blue-white hue and contained a small pocket of air, which at certain angles produced a rainbow, or Newton's rings.
Petra Diamonds
Petra Diamonds Ltd is a diamond mining group headquartered in Jersey. It has a diversified portfolio, with interests in eight producing mines in South Africa and Tanzania and an exploration programme in Botswana. Petra Diamonds' focus has shifted from exploration to production, becoming one of the largest independent producers of diamonds in Africa. In June 2012, Petra owns 5 of the world's most productive mines historically. These mines include the Cullinan Diamond Mine famed for having produced the world's largest rough and polished diamond. It is listed on the London Stock Exchange.