SANTIAGO, Jun 30, 2010 (Dow Jones Commodities News Select via Comtex) --
 
Chilean copper output retreated 5.4% in May from the same month a year ago to 430,736 metric tons from the 455,304 tons produced in May 2009, the government statistics agency reported Wednesday.

In the first five months of the year, Chile produced a total of 2,155,106 tons of the red metal, up 1.3% from the 2,126,400 tons it mined in January-May 2009.

Last year, Chile produced 5,408,561 tons, up 0.8% from 2008. That is equivalent to about 35% of global copper production.

The statistics institute, known by its Spanish acronym INE, said the decrease was likely transitory as it was due to one-time labor issues and unscheduled equipment maintenance, although it didn't specify where these production problems occurred.

The South American nation produces over a third of the world's annual copper supply.

The production of copper contained in concentrates retreated 18.1% in May from a year earlier to 161,450 tons, the INE said. Output of copper cathodes inched up 1.6% to 235,467 tons, the institute said.

Cathodes, which are large sheets of 99.99% pure copper, have a higher added value than concentrates, as concentrates must be smelted or refined to get the purer form of the metal. The country also produces other forms of copper, such as blister, but in very small amounts.

Chile is the world's largest copper producer and also one of the leading molybdenum, iodine, lithium, gold and silver producers. The mining industry represents about 20% of the country's gross domestic product, according to the government's most recent data.

The country's molybdenum output in May totaled 3,015 tons, a 12.1% surge from the 2,689 tons it produced the same month a year ago.

January-May molybdenum output fell 3.5% to 13,422 tons from the 13,906 tons produced in the first five months of 2009.

May gold production fell 10.1% and silver production slid 10.7%, the INE reported without providing output figures. Both precious metals are often found as byproducts at many Chilean copper mining operations.

Iron ore production plummeted 16.9% from a year earlier, the INE said without providing the amount of tons produced.