Copper ended up on Thursday for only the second time this month but posted its biggest daily gain in nearly nine months, as positive economic signals in the world's top-two consumers powered the rally. In New York, the key September COMEX contract jumped 12.00 cents or by 3 percent to settle at $4.0085 per lb, near the upper end of its $3.8560 to $4.0360 session range.
Reuters Commodities Specialist Christopher Henwood said any slowdown in global economic growth will push copper below key support levels as low as $3.40. The rally helped drive COMEX copper volumes up about 40 percent from the 30-day norm, at 66,500 lots, but well away from last Friday's record 98,079 lots.