Sir Ernest Oppenheimer (22 May 1880 – 25 November 1957) was a diamond and gold mining entrepreneur, financier and philanthropist, who controlled De Beers and founded the Anglo American Corporation of South Africa.
He was born in Friedberg, Germany, the son of Edward Oppenheimer, a cigar merchant. Oppenheimer began his working life at 17, when he entered Dunkelsbuhler & Company, a diamond brokerage in London. His efforts impressed his employer and in 1902, at the age of 22, he was sent to South Africa to represent the company as a buyer in Kimberley, where he eventually rose to the position of mayor in 1912. 
He became great friends with William Lincoln Honnold, an American engineer and chairman of Transvaal Coal Trust, Brakpan Mines, Springs Mines and The New Era Company. 
In 1917, they launched the Anglo American Corporation with financial assistance from J. P. Morgan. The initial capital was £1 million. Half of the capital was subscribed in America and half in England and South Africa.
In 1927, Ernest Oppenheimer managed to wrest control of Cecil Rhodes's De Beers empire and built and consolidated the company's global monopoly over the world's diamond industry until his retirement.
He died in Johannesburg in 1957. He was born into a Jewish family, but as an adult, he converted to Anglicanism and was buried at St George's Church, Parktown. He was succeeded in the business by his son Harry Oppenheimer. Oppenheimer's brother, Sir Bernard Oppenheimer, was also heavily involved in the diamond industry.
In 1964, the Oppenheimer Diamond was named in his honour by its owner, Harry Winston, who donated the stone (not a gem, as it remains uncut and unpolished) to the Smithsonian Institution as a memorial.
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- H. F. Oppenheimer, R. B. Hagart, W. D. Wilson, Francis Whitmore, H. MacConachie, Dr. J. E. Holloway, Optima, September 1967 Volume seventeen number three, Commemorates the Fiftieth Anniversary of Anglo American Corporation September 25th 1967, p.97.
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- [http://www.sahistory.org.za/pages/people/bios/oppenheimer-e.htm Sir Ernest Oppenheimer @ South African History Online
- History of Sir Ernest beginnings @ De Beers
- Biography Ernest Oppenheimer online version Gregory, Ernest Oppenheimer and the Economic Development of South Africa, Cape Town University Press, New York, 1965
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