PolyMet Mining seems an unlikely candidate to launch North America's next mineral boom. In its 33 years of existence, it hasn't mined a single ounce of marketable ore. Yet Jon Cherry, an environmental engineer and PolyMet's chief executive officer, says the company's profitless days are numbered, thanks to technology he says can squeeze big amounts of difficult-to-extract copper and nickel from the eastern edge of the historic Mesabi Iron Range. PolyMet says its copper deposits, on land about 65 miles north of Duluth, MN, alone could be worth more than $10 billion. Mining companies have long known the Duluth Complex is rich with metals. But the difficulty and expense of freeing the coveted ores have always frustrated their dreams. Pollution could persist for decades beyond the mine's planned 20 years of use. That's put PolyMet in the middle of a fractious jobs-vs.-environment battle in Minnesota. Environmentalists fear that fouled rock and water could threaten drinking water, as well as habitats for wild rice, fish, and other species