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Copper and nickel deposits show promise, but no paydirt in Carlton, Aitkin counties

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Copper and nickel deposits show promise, but no paydirt in Carlton, Aitkin counties
Farmington Minnesota P.O. Box 192 / 312 Oak St. 55024

It's just a little purple squiggle on a map of Minnesota's bedrock, a long, thin arc that cuts across the Carlton and Aitkin county lines.

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The squiggle might turn out to be nothing. But geologists with Utah-based Kennecott Exploration Co. have been drilling holes along that squiggle since 2001 in an effort to determine just what might be down there, and whether it might be worth digging up.

The company is looking for mineable copper and nickel deposits, one of three or four similar explorations Kennecott has under way, project geologist Robert Peter said. In Carlton County, "We've had encouraging results, but we haven't had dramatic or exciting results," he said.

That means the company has found enough to keep them looking, but not enough to take the next step towards developing a mine -- yet.

While it's long been known that Northeastern Minnesota has rich deposits of iron ore, companies now are focusing attention on deposits of copper, nickel and other precious metals as they become more valuable on the world market. Canadian-based Franconia Minerals Corp., PolyMet Mining Corp. and Oakdale, Minn.-based Duluth Metals Corp. all are exploring or planning to mine metals deposits on the Iron Range.

And all of those companies are in Minnesota because of something that happened more than a billion years ago.

About 700 million years before dinosaurs appeared on Earth, what is now North America began to split apart along a line that stretched from what is now Kansas northeast toward Lake Superior and Lake Michigan. As the continent began to break apart along this rift, magma welled up through cracks in the bedrock, carrying deposits of copper, nickel and other metals from deep within the Earth. Eventually, the rift stopped splitting, and most of that magma solidified into bedrock.

But in some places, the magma mixed with sulfur deposits and turned into pyrrhotite, a bronze-colored, metallic mineral -- and that's just what Kennecott, Polymet and plenty of other companies are looking for.

What's interesting about the formation, Peter said, is that it looks different from everything else around it.

A map of Minnesota's magnetic rock formations shows a number of colorful arcing lines covering the center of the state. Each arc depicts bedrock of varying magnetic strengths curving north and east in a graceful wave. But right around Tamarack in Aitkin County and Cromwell in Carlton County, a short squiggle of purple -- indicating strong magnetic qualities -- arcs the other way. That's the kind of anomaly geologists look for, because it means something happened there that could have concentrated the copper and nickel deposits.

"We don't know what is there," Peter said. But each of the 40 or so bore holes Kennecott has sunk tells them something, and that's why geology graduate students and future husband and wife Jenny Koester and Brian Goldner of Duluth pore over each drill core that comes out of the ground.

They will measure the rock's density, glue together any shattered core samples and use hand lenses to examine the crystalline structures in the rock. Samples of rock are ground into powder and chemically analyzed for traces of copper and nickel, and each core sample is marked, boxed and labeled for permanent storage at a Minnesota Department of Natural Resources center in Hibbing.

It's meticulous and interesting work, they said.

"We get to look at rocks that no one has seen for 1.1 billion years," Goldner said.

Each box of core samples that comes to the lab "is like opening a present," Koester added.

Kennecott moved their field laboratory from McGregor to an empty machine shop in Tamarack in late 2006. They have since opened their laboratory doors to anyone interested in the operation in an effort to remove any mystery surrounding the project, Peter said. In early January, the company also sent letters outlining their exploration plans to residents.

Some people have stopped by with concerns about the long-term environmental effects of mining copper and nickel, most notably sulfuric acid leaching out of the waste rock. Some have wondered about the potential for new jobs in the area, while others are simply curious, Peter said.

Explorations similar to Kennecott's work are going on throughout Northeastern Minnesota. In 2007, the DNR put 52 leases on state land totaling 16,732 acres up for competitive bid. Kennecott won six of those bids, while three other companies went after leases in Lake, St. Louis, Kanabec and Mille Lacs counties.

The state of Minnesota controls the mineral rights on about 12 million acres of Minnesota's 51 million acres. Each year, based on the amount of interest in exploring for minerals, the state puts certain properties up for lease, said David Dahlberg, a geologist with the DNR's division of lands and minerals.

All the data that Kennecott collect from their Carlton County and Aitkin County sites are kept confidential while they are actively exploring.

If and when the company stops drilling, that data will become public knowledge, just like the core samples become public property owned by the state.

It won't be until this year's samples are fully analyzed that Kennecott will decide whether to continue exploring, Peter said.

"This winter could be the end, the company could decide its money is better spent elsewhere," Peter said. In the business of mineral exploration, "You've got to believe there is a possibility [of finding a deposit], but you also have to know when to let go."

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