Twin Metals, the company that is proposing an underground mine and processing plant in Minnesota said the property contains 19 percent more gold, copper and palldium than previously estimated.
The project would make Minnesota home to one of the world's largest deposits of precious metals, the Star Tribune reported.
“These are not minor mineral holdings,” said Bob McFarlin, vice president for government and public affairs for Twin Metals, a partner in the planned project, which released the results of the new geological analysis. “The state is sitting on an absolute economic juggernaut for generations to come.”
Twin Metals is a joint venture between Duluth Metals, a Canadian company, and Antofagasta PLC of Chile.
Located along Hwy. 1 near the Kawishiwi River, it is expected to cost $3 billion and eventually could employ hundreds, Twin Metals said.
The value of the mineral wealth in the area was pegged last summer at more than $100 billion. The new estimate assigned high confidence to the presence of 13.7 billion lbs of copper, 4.4 billion lbs of nickel and 21.2 million oz of palladium, platinum and gold. The platinum and palladium deposits would be one of the largest outside of South Africa.
The project, along with a proposed mine run by PolyMet Mining Corp., has raised alarms among environmentalists, who worry about the potential impact on northern forests and lake country. PolyMet, which plans a $600 million openpit project near Hoyt Lakes, is now preparing for the environmental approval process, which it expects to start next year.
Both PolyMet and Twin Metals said they expect to meet all state and federal environmental standards. PolyMet said this summer that it had installed a reverse osmosis water treatment system to remove all contaminants from water.
Twin Metals hopes to complete a pre-feasibility study for the mine, which will include baseline environmental data, sometime in 2014.
As it completes increasingly extensive engineering and geological surveys, Twin Metals has consistently raised its estimates of the deposits within its holdings. But this latest increase, an average of 19 percent more copper, gold, nickel and palladium, was significant. McFarlin said it reflected both the breadth of the deposit and the concentration of ores within the rock.