Brazil-based Vale (VALE.NYSE, VALE3.SAO), the world’s largest producer of iron ore, may raise its bid for South African copper miner Metorex (MTX.SJ) in response to a US$1.36 billion bid from Chinese nickel producer Jinchuan Group, Bloomberg reported. The bid is 21% higher than Vale’s original bid; if the bid is accepted, or exceeded by Vale, it would be the most expensive acquisition of a diversified minerals company in history. Vale has until July 15 to match or beat Jinchuan’s offer, Metorex said. Acquisitions in the copper industry are on the rise after prices for the metal doubled in the last two years. Vale is considering the future trajectory of copper prices before making its bid, and the company has said it has a price limit and will not engage in a bidding war. However, Leonardo Brito, an equity analyst in Rio de Janeiro, said that Vale is likely to increase its bid given that Metorex’s valuation is still relatively low, given its market value and cash position.