Anglo-American, the FTSE-100 global mining company is, according to reports, under pressure to take over the diamond firm De Beers.The Observer claims some Anglo shareholders feel its current 45% stake in De Beers is undervalued. If it bought a majority stake it could then be transparent about how much the firm is worth and possibly extract more value.This would involve buying out the billionaire Oppenheimer family who have owned the company since the 1920s, although the political situation in South Africa may persuade them that some kind of transaction would help hedge against political instability.Anglo-American shares were flat in early trading.BS