The key March COMEX contract dropped 5.60 cents or nearly 1.6 percent to settle at $3.50 per lb on Thursday, close to the bottom end of its $3.4790 to $3.6045 session range. Futures picked up a bit from earlier in the week, but with about 47,000 lots traded in late New York business, volumes stood nearly 20 percent below their 30-day norm, according to preliminary Thomson Reuters data.