COMEX copper futures closed mostly a touch softer Friday in thin but volatile trade in which prices briefly surged higher on a rumour of a supply disruption in Indonesia, traders said.
Active July copper fell 0.10 cent to $1.1780 a lb, after trading from $1.1960 to $1.1670. Spot May lost 0.15 to end at $1.1760.
Deferred months were from down 0.10 cent to up 0.10 cent.
Benchmark July futures briefly jumped to a session high just below $1.20 a lb in New York and $2,620 a tonne in London on talk in the market that Freeport-McMoRan Inc's Indonesian Grasberg copper and gold mine, the world's third largest copper mine, had experienced supply disruptions.
Freeport denied any such event, but said work at the pit had been suspended briefly on May 11 for safety reasons after heavy rain.
"I think Grasberg's why we popped up this morning before we came off a bit," said one New York desk broker.
Aside from the rumour, trading focused on the day's mixed batch of US economic data, he said, noting prices finally declined in late activity as traders digested that.
Another trader, at the COMEX floor, said scattered stop- loss buying ran into resistance at $1.20, basis July futures.
Brokers peg resistance in COMEX July at $1.1950 and $1.20 followed by $1.2250, with support at $1.1650 and $1.15.
Estimated volume was 9,000 contracts, up from Thursday's 7,249 lots. Open interest rose 13 to 63,760 lots.