The December contract for gold futures fell $20, or 3.2%, to close at $597.30 an ounce Monday. That marked its lowest level since June 28, with the weakness reflecting the broad decline among commodities prices. December silver dropped $1.055, or 8.6%, to close at $11.24 an ounce, a level it hasn't seen since July 26. December copper fell 15.05 cents, or 4.2%, to end at $3.4175 a pound.