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.
Economic confidence, which has been savaged in recent days from a credit rating downgrade in the United States and concerns over a spreading debt crisis in Europe, was partly restored after an appreciation in the Chinese yuan and relatively positive US labour market data struck a rare optimistic tone in the broader market.
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. 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.