Comex copper futures climbed two percent on Friday, boosted by a late bout of speculative buying following news that workers at the Escondida copper mine began their vote to strike, sources said.
"We saw the buying pick up later in the day as news started to trickle down on the floor that they began their vote, but I think you have to be careful ... it may be a 'buy the rumour, sell the news' type scenario," said one COMEX copper dealer.
"We'll get a better understanding on where this market stands next week when we see if there will actually be a strike or not, but for now it looks likely," he added.
Copper for September delivery ended up 7.05 cents, or 2 percent, at $3.5490 a lb on the New York Mercantile Exchange's COMEX division, near the top of its $3.44 to $3.56 trading band.
"I think we're still in a bull market. We had a pretty good sell-off down to that $3.20 level last Monday and it's been boosted ever since. It's still within the range that I kind of think it will stay in, between $3.20 and $3.70, but this is a good settlement for a Friday and definitely sets the stage for maybe $3.70 next week," said Scott Meyers, senior trading analyst with Pioneer Futures. The now spot August contract rose 7.55 cents to $3.5840, just off its session peak at $3.5850. COMEX final copper volume was estimated at 10,000 lots, in line with the 10,099 lots recorded on Thursday.