SAN FRANCISCO (MarketWatch) -- Gold prices closed lower Tuesday as negative U.S. economic news made for skittish investors in bullion and copper, which also came under pressure from a spike in London inventories. A few mining companies' shares got a lift, however, on rumors of a link-up between Newmont Mining Corp. (Last: 41.07+0.62+1.53%) and Barrick (-4.1%), which later squashed that speculation.