Copper mining giant Antofagasta reported a 29.2 per cent fall in earnings in the first quarter reflecting lower commodity prices and higher operating costs.Earnings before tax, interest, tax, depreciation and amortisation (EBITDA) came to $781.7m in the first three months, compared to $1.1bn the previous year.Revenues fell 14.6% to $1.5bn from $1.7bn as prices of copper and gold dropped during the quarter. The realised copper price in the period declined from $4.29 per pound in the first quarter of 2012 to $3.41 per pound this year.Market gold prices averaged $1,632.1 per ounce, a decrease from the average price of $1,690.9 per ounce in first quarter of 2012.Copper production rose 12.8% to 183,800 tonnes from 162,900 tonnes thanks to higher plant throughput at the Esperanza mine in Chile. Sales volumes rose modestly in comparison to production at 170,000 tonnes, up from 158,700 tonnes the prior year, as the company was hit by temporary delays in shipping due to strikes at ports from which El Tesoro and Michilla's copper production is transported.Gold production volumes increased to 86,200 ounces from 63,500 ounces while sales climbed to 74,800 ounces from 63,400 ounces, driven by increased production at Esperanza.The group ended the period with net cash of $2.6bn, up from $2.5m at the end of the previous quarter. RD