Gold prices closed lower on the Comex division of the New York Mercantile Exchange Thursday. Comex gold dropped 1 percent as it gave up $16.80 to hit $1,669.90 per troy ounce. Silver shed 72 cents or 2.2 percent to close at $32.72 an ounce. Equities were mixed on Wall Street. The dollar index was essentially flat, rising 0.01 percent to 79.97.