Rio Tinto said on Wednesday it had failed to arrest a decline in the United States and Australia in mined copper output, which fell 6 percent in the third quarter because of lower metal content in its ore, driving its Australian share price down.
Coal output was also lower at a time of high demand, with steel mills and power generators vying for limited supplies.
"It was a surprise to see almost everything down," said ABN Amro analyst Warren Edney.
The world's third largest miner by market capitalization reported a 30 percent rise in third-quarter refined copper production as it tried to capitalize on the global boom in industrial raw materials.
Rio shares closed down 3.5 percent at A$110.00, outstripping an 0.18 percent loss on Australia's S&P/ASX200 index.
Aluminum production was flat over the quarter, the company said.
Copper, found in everything from water taps to computer chips, is a key component underpinning analysts' profit forecasts of around $7.4 billion for the Sydney and London-listed company, accounting for nearly half of first-half profits.
Copper for delivery in three months on the London Metal Exchange has soared more than 25 percent this year to above $8,000 a ton, spurred on by high imports to China.
Iron ore was a distant second at 29 percent of first-half earnings, with aluminum providing 11 percent of earnings during the period.
Rio's 30 percent stake in the Escondida copper mine in Chile, the world's biggest, delivered 101,200 tons of contained copper and 16,100 tons of refined cathode.
Aluminum output was set to soar in 2008 to more than 4 million tons when Rio completes its $38.1 billion acquisition of Canadian producer Alcan to create the world's largest aluminum company.
Rio said its iron ore production and shipments in the third quarter were near record levels, with output in Australia 11 percent ahead of 2006 for the first nine months of the year.
Rio, close rivals CVRD, BHP Billiton and a number of smaller miners, are poised to see a boost in selling prices for iron ore next year following negotiations with steel mills, based on analysts forecasts.
"Looking to the next round of negotiations, we are increasingly confident of a windfall outcome for the miners," Macquarie Bank said in a report, predicting a price rise of 50 percent ore more next year.
Congested shipping ports and railways in eastern Australia hurt third-quarter coal production, reducing hard coking coal output 10 percent and thermal coal production 24 percent.