Jiangxi Copper, the largest mainland producer of the metal, said its first-half earnings more than doubled, thanks to rising copper and gold prices, as well as increased sales. Net profit for the six months to June climbed to 2.09 billion yuan or 72.2 fen per share, up 114 per cent from 974.55 million yuan or 36.58 fen per share a year earlier, in line with market expectations. Sales increased 37 per cent to 9.49 billion yuan. 'The demand and supply of copper worldwide remained tight [in the first half] albeit the global output of copper increased,' Jiangxi Copper chairman He Changming said. Copper futures rose to a record US$8,800 a tonne on the London Metal Exchange in May, and have more than doubled over the past year. Copper prices were steady yesterday after rising almost 3 per cent on Monday, supported by a prolonged strike at the world's biggest copper mine, Escondida, in Chile. 'Copper prices have peaked,' said Alexander Latzer, an analyst at Merrill Lynch, who has a 'sell' rating on Jiangxi Copper on concerns that prices may fall to affect the company's margin. Jiangxi Copper produced 1 per cent more copper cathode in the first half from a year ago to 228,900 tonnes. It also produced 7 per cent more gold to 6,689 kilograms and 1 per cent less silver to 175 tonnes. Copper and related value-added products made up about 85 per cent of Jiangxi Copper's revenue while precious metals including gold and silver accounted for 11.5 per cent. The company said its gross profit margin gained 15 percentage points in the first half to 40 per cent as copper and precious metal prices surged. However, it booked a 1.34 billion yuan loss from its short position on copper futures due to the increase in prices. Jiangxi Copper bought futures to hedge against volatility in raw material costs. With the increasing demand and the uncertain supply due to strikes and shrinking reserves, the company said global copper prices would remain high in the second half. Jiangxi Copper, which controls 17 per cent of China's copper output, aims to lift annual smelting capacity by 75 per cent to 700,000 tonnes by June next year after a 3.4 billion yuan, four-phase expansion of its Guixi smelting plant. Shares in Jiangxi Copper gained 2.84 per cent to close at HK$7.60 yesterday before the earnings announcement.