Antofagasta's revenues in the first half dropped 12.1 per cent to 2.7bn dollars, reflecting a decline in copper prices and increased costs. Earnings before interest, tax, depreciation and amortisation (EBITDA) fell 31.2% to $1.2bn following the average London Metal Exchange price of copper falling by 6.8% and realised copper prices sliding 15.5%.Group net cash costs were up 27.3% to $1.26 per pound as a result of lower molybdenum volumes and lower molybdenum and gold prices.Nevertheless, the group achieved an 8.4% rise in copper production to 364,100 tonnes and a 9.7% increase in gold production to 162,900 ounces.Chief Executive Officer, Diego Hernandez, said the company remains on track to achieve full year production target of 700,000 tonnes of copper."Market conditions remain challenging with lower prices and higher costs impacting our revenues and profitability," he said."However, cash generation by the business was strong and the interim dividend has been increased by 4.7% to $0.089."Net cash at the end of the period was up 12.5% to $1.5bn. Hernandez added that the miner would concentrate of controlling unit costs and optimise production from existing operations. The optimisation of the Esperanza mine is on track with average throughput of 86,700 tonnes per day achieved and expected to reach 105,000 tonnes per day in 2015. Esperanza recently satisfied the completion test under the project financing agreements and the debt is now non-recourse to the company. RD