* Substantial part of proceeds earmarked for Africa
* Oppenheimers among Africa's richest
* Family involved for over 80 years
By Marius Bosch
JOHANNESBURG, Nov 4 (Reuters) - For over 80 years, South Africa's Oppenheimer family held sway over the global diamond trade, an era which came to an end of Friday with Anglo American's buyout offer for De Beers.
The $5.1 billion the family will get for its 40 percent stake in the diamond giant could see a large chunk ploughed back into Africa for private equity investment or philantropic work in the world's poorest continent.
The Oppenheimers have been involved at De Beers since 1927, when Ernst Oppenheimer, who founded Anglo American a decade earlier, took control of the group.
The family's fortune has been intertwined with South Africa's history and economy ever since.
"At the end of the day this has been a very momentous decision for the family. We didn't approach Anglo, Anglo approached us," said James Teeger, managing director of family holding company E. Oppenheimer & Son.
The world's largest diamond miner, De Beers was established in 1888 in South Africa. Its corporate slogan 'A diamond is forever' was created in 1947 and named the greatest advertising line of 20th century by Advertising Age magazine.
De Beers Chairman Nicky Oppenheimer, educated at Harrow and Oxford, is a passionate cricketer who has his own cricket ground outside Johannesburg. He has been at the helm since 1998 and his father Harry was chairman of De Beers for 27 years until 1984.
Anglo American has been trying to buy the family's stake for years but the Oppenheimers declined to sell -- even when the 2008 global financial crisis forced shareholders to pump cash into De Beers when diamond sales and demand for luxury goods plunged.
Since then analysts said the Oppenheimers sought to step up the pace of diversifying their investments.
The deal happened very fast, Teeger said, adding that diversification was one of the factors which convinced the family to sell.
"This thing happened extremely quickly, (Anglo chairman) John Parker approached Nicky Oppenheimer a few weeks ago, literally three of four weeks ago."
The speed of the transaction meant the family had no specific plans on how the capital will be deployed.
"The one thing for sure is that we are going to deploy a substantial amount of the capital in Africa," Teeger said.
The Oppenheimer family holding company already has a private equity arm operating in South Africa, investing in mid-sized firms.
In August it set up a $300 million private equity fund with Singapore state investor Temasek Holdings to invest primarily in consumer goods and agricultural sectors across Africa.
The transaction brings to an end the era when the global diamond trade was driven by relationships between a small group of people, said Martin Rapaport, Chairman of the Rapaport Group, and a well-known commentator on diamond industry developments.
"This is the final vestige of a time when a community of people working together directed the industry," he said.
De Beers tightly controlled the diamond market for decades before changing its strategy in 2000, buying up and stockpiling diamonds to control gem prices.
For the Oppenheimers, worth around $7 billion according to Forbes magazine which put them in 136th place of the world's billionares, not much will probably change after the De Beers sale.
They are passionate conservationists and own the Tswalu Kalahari Reserve, the largest private game reserve in South Africa.
Their Brenthurst mansion in Johannesburg is famed for its gardens which have been opened to the public and the family is involved in numerous charity and upliftment projects in South Africa.
Nicky Oppenheimer told South Africa's Mining Weekly trade publication last month that relaxing is his hobby.
And when asked what his personal best achievement was, he replied: "Choosing my parents very well".