SAN FRANCISCO (MarketWatch) — Gold futures on Monday suffered their biggest one-day decline since the 1980s, as the metal extended its dive into a second straight session and pushed further into bear-market territory.

The broader metals complex also dropped, with silver down 11% for its lowest settlement in more than two years after disappointing Chinese data fed worries over industrial metals demand.

Mining firms were hard hit by the selloff, with shares of Freeport-McMoRan Copper & Gold Inc. (US:FCX) dropping 8.2% and Newmont Mining Corp. (US:NEM) down 5.8%, as resource stocks led the S&P 500 index (US:SPX) lower Monday afternoon.

Gold for June delivery (US:GCM3) tumbled $140.30, or 9.3%, to $1,361.10 an ounce on the Comex division of the New York Mercantile Exchange. Prices dropped to as low as $1,355.30.