The two firms weighing rival bids are said to be Chinalco Mining Corp International, a subsidiary of China's state-run aluminum group, and Hong Kong-listed MMG Ltd.
Iron ore, molybdenum and nickel are the main commodities executives see as having the highest likelihood of depreciating in value over the next three years.
Capital expenditure in mining peaked last year, stabilized in the second half of 2012 and then plunged steeply in the March quarter, wiping almost $1.5 billion off Australia's quarterly output.