Swiss mining group Xstrata said Tuesday it had a strong first quarter despite lower output in some sectors. \"Our operating and financial performance continues to be strong and the company\'s financial position remains robust,\" the company said in a trading update. Xstrata said copper production for the quarter fell 18 percent compared to the first three months of 2011, while output of the stainless steel additive ferrochrome was down 20 percent. Coal production was up nine percent and nickel eight percent, while zinc output held steady, it said. The company gave no first quarter financial details. Xstrata is in the process of joining forces with Swiss commodities giant Glencore after the two announced plans for a merger that would create a $90-billion (68.4-billion-euro) raw materials behemoth. The deal is expected to be finalised in the third quarter of 2012.