The company planning an underground copper, nickel and precious metals mine near Ely in northeastern Minnesota boosted its estimates Tuesday of the reserves the site holds.

Toronto-based Duluth Metals Ltd., the parent company of Twin Metals Minnesota LLC, said its final estimates are an average of 19 percent higher than an interim estimate the company issued in June, when CEO Christopher Dundas called it a "monster deposit" and estimated the value of the metals at more than $100 billion.

The company will use the data as it develops a detailed plan for the Twin Metals mine, which it plans to build eventually just east of Birch Lake, about 15 miles southeast of Ely. Twin Metals has said its $2 billion project would create hundreds of jobs, but any actual mining is years away.

The new estimate is based on data from additional drill holes, which confirm that the Twin Metals resource is one of the largest copper-nickel-precious metals deposits in the world and one of the largest platinum and palladium resources outside South Africa, the company said in its statement. One highlight of the report was sharply higher estimates for platinum, palladium and gold.

According to the new estimate, the site contains "indicated resources" of 13.7 billion pounds of copper, 4.4 billion pounds of nickel and 21.2 million ounces of palladium, platinum and gold. The company has high confidence in those estimates because they're based on samples from a high number of drill sites. It separately projects "inferred resources" of 11.


8 billion pounds of copper, 4 billion pounds of nickel and 12.8 million ounces of precious metals, but those estimates are less certain because they're based on fewer samples.

One of the next major steps is a "prefeasibility study" the company is conducting to lay the foundation for the mine plan and its environmental reviews. Duluth Metals spokeswoman Mara Strazdins said they expect to complete it sometime in the first half of 2014.

Twin Metals is a joint venture between Duluth Metals, which owns 60 percent, and Chilean mining company Antofagasta PLC, which owns 40 percent.

Another company, PolyMet Mining Corp., which is developing an open pit mine for the same metals mine near Hoyt Lakes, is further along in the planning and regulatory process, but Twin Metals would be a much larger project.

Supporters of the projects say the potential new copper-nickel-precious metals industry in northeastern Minnesota would bring badly needed jobs to a region where the economy is now heavily based on iron mining, forestry and tourism. But environmental groups have teamed up to fight the projects because the minerals are bound up in sulfur compounds that can leach sulfuric acid and other contaminants when exposed to the elements, and they fear the runoff could reach the Boundary Waters Canoe Area Wilderness and Lake Superior.