Comex copper has tumbled on speculative liquidation, with technical selling contributing to the decline, says a trader. Selling was triggered as the market broke down through its lows the last two days around $3.5350, he says. "Now we're into another chart support area around $3.49 to $3.50," he continues. The market put in several daily lows around here earlier this month. Some of the weakness is in part due a stronger dollar and softer crude and precious metals, the trader says. Another trader says that metal in London - which tends to lead Comex - may have been at least partly influenced by news that margins will rise for LME copper and certain other base metals next week. However, most of the focus appears to be on technicals, he adds, with three-months copper in London unable to generate momentum above recent highs around $8,100 a ton. Comex July copper is down 11.35 cents to $3.4920.