By Alexandra Stevenson and Javier Blas

Anglo Americanhas agreed to pay the Oppenheimer family $5.1bn to take control of De Beers, the world?s biggest distributor of diamonds, in a sign that deal activity in the mining industry is beginning to pick up after months of falling share prices.

The UK-listed mining company said on Friday it is to buy a 40 per cent stake in the South African diamond company, in a deal that comes as Anglo American is set to lose control of a key copper asset in Chile.

?This transaction is a unique opportunity for Anglo American to consolidate control of the world?s leading diamond company – De Beers,? said Cynthia Carroll, Anglo American?s chief executive said in a statement.

The move is the clearest sign yet that the recent fall in mining sector valuations has flushed out corporate predators. At a recent gathering of the sector in London, mining executives and bankers said that share price falls had created an opportunity for cash-rich miners to buy up scarce natural resources near the bottom of the cycle.

Under a current agreement between CHL, a holding company which represents the Oppenheimer?s interests, Anglo American and the Botswanan government, the African state has the pre-emption rights to increase its holding up to 25 per cent should it wish to do so.

In the event that Botswana exercises these pre-emption rights, Anglo American would acquire an incremental 30 per cent interest in De Beers, taking its total interest to 75 per cent, and the consideration payable by Anglo American to the CHL would drop proportionately.

?Anglo America has struck a very good deal for itself,? said Dominic O?Kane, mining analyst at Liberum Capital in London said. At $5.1bn the miner would pay 5.6 times the expected earnings before interests, taxes and depreciation for De Beers in 2012, well below the 8.5-9.8 level at which listed peers such as Petra and Gem Diamonds trade.

Mr O?Kane said that shareholders had been ?clamouring? in recent years for Anglo American ?to either increase its stake in De Beers or to IPO its stake.?

Earlier this year Ms Carroll downplayed speculation that the miner was on the look-out for acquisitions but said prices were still ?too high?.

Asked why Anglo American did not increase its stake in De Beers when the diamond producer struggled during a downturn two years ago, Ms Carroll said: ?Where there is a buyer there has got to be a seller – that is the bottom line.?

The deal will mark an exit for the Oppenheimer family from De Beers, the 74-year old company in which it was an early shareholder. Analysts said on Friday that the decision to sell was probably linked to succession of Nicky Oppenheimer, the family business chairman, who stepped down from the Anglo board earlier this year.

The deal comes as Codelco, the state-owned Chilean miner, has told the London-listed miner it intends to exercise a longstanding option to purchase 49 per cent of Anglo Sur, a group of copper assets that includes the Los Bronces mine, for no more than $6.75bn. Anglo American has invested nearly $3bn in recent years to develop Los Bronces.

The company said it would seek approval from shareholders at the next extraordinary general meeting expected to take place before Christmas. The transaction is also subject to regulatory approval.

Anglo shares, which have fallen more than 20 per cent in the last six months, opened 40?p or 1.7 per cent higher

at ?23.97.

? The Financial Times Limited 2011