SYDNEY (AP) â¿¿ BHP Billiton, the world's biggest mining company, said Wednesday its chief executive Marius Kloppers will retire in May. The company also announced a 58 percent fall in half-year profit. Kloppers is the second CEO of a major mining company to resign since January. Rio Tinto PLC chief executive Tom Albanese resigned suddenly last month after the company announced a big loss on a recent acquisition in Mozambique. Kloppers will be replaced on May 10 after six years at the helm by the chief executive of BHP's non-ferrous metals division, Andrew Mackenzie, 56. BHP Billiton chairman Jac Nasser said Kloppers guided the mining giant through the global financial crisis. "Despite an exceptionally difficult environment during his tenure, Marius and his team have delivered for shareholders, significantly outperforming our peers in terms of total shareholder returns," Nasser said in a statement. "He drove new investments into next generation opportunities including U.S. onshore gas and liquids and created one of the most valuable companies in the world," he said. Mackenzie has deep industry knowledge and global management experience, Nasser said. Mackenzie held senior positions with Rio Tinto before joining BHP Billiton in 2008. The announcement of Klopper's resignation came as the Anglo-Australian company posted a 58 percent fall in first half profit to $4.24 billion due to lower commodity prices and a weak U.S. dollar. The net profit for the six months to Dec. 31, 2012 was down from $9.94 billion a year earlier. The latest result included $1.4 billion in one-time costs from asset sales. Profit excluding one-time items was $5.7 billion, down 43 percent from $9.94 billion the year before, due to falls in iron ore and other commodity prices in 2012. Analysts had expected a net profit excluding one-time items of $5.69 billion.