For more than a decade, copper-sulfide mining has been one of the most contentious environmental debates in Minnesota.

Environmentalists maintain that copper-sulfide mining, which has never been done in Minnesota and is much different than traditional iron mining, would cause permanent damage to the water-rich environment of Northeastern Minnesota. Proponents of these mines argue that they will create jobs and provide a much-needed economic boost to the region.

The debate has just taken a new turn. PolyMet, which would be the first copper-sulfide mine in Minnesota, recently announced it will file a preliminary prospectus for rights offering with regulators and enter into a standby purchase agreement with Swiss-based Glencore. Financial and legal jargon aside, this means Glencore, which already owns 28.8 percent of the company, might be able to buy a majority share, allowing it to control PolyMet.

Who is Glencore and why should Minnesotans be concerned about this company potentially operating a copper-sulfide mine in our state?

As one of the largest commodities traders and mining companies in the world, Glencore has a reputation for aggressive tactics that stretch ethical and legal norms. It has been accused of manipulating the global aluminum market by hoarding supplies, engaging in secretive campaigns to undermine renewable-energy initiatives, dumping raw acid into a community’s water supply, and exploiting child labor. The company also reportedly has been involved in a bribery scandal that shook top tiers of the Brazilian government and currently is under investigation by the U.S. Justice Department for allegations of bribery and money laundering.

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Additionally, Glencore is notorious for squeezing workers. When Glencore acquired Sherwin Alumina in Texas, it began to slash wages and benefits. New workers were no longer given pensions, disability payments, or even widow’s benefits. When workers represented by United Steel Workers pushed back, they were shut out for two years and replaced by contract workers. Ultimately, Glencore closed the plant.

Throughout the developed world, workers have had to go on prolonged strikes to prevent Glencore from gutting their benefits and pay. In Australia, Glencore locked out miners from its Oaky North mine for 230 days. At Glencore’s CEZinc refinery in Canada, 371 workers had to go on strike for almost 10 months to stop a raid on their pensions.

In Minnesota, can workers expect to be treated any differently? What’s more, how many people from the Iron Range will the PolyMet mine truly employ? Officially, PolyMet says 360. There are reasons to doubt that.

Like every industry, mining has been transformed by automation, which has cut the need for human workers. According to a study of the Arizona copper industry, from 1974 to 2003, the number of workers it took to produce 1,000 tons of copper plummeted by 80 percent. Since this study was conducted 15 years ago, automation has advanced exponentially. You can bet that Glencore, currently ranked as the 14th-largest company in the world, uses sophisticated automated processes to maximize output and minimize labor costs. This may be good for investors’ portfolios, but it likely won’t be good for Minnesota workers.

We may soon have one of the wealthiest, most powerful, and most corrupt companies in a position to control an incredibly toxic and dangerous mine in our state. When one takes into account the already high cost of mining Minnesota’s low-grade copper deposits, the reality of automation, Glencore’s record of squeezing workers and fighting labor, and the fact that PolyMet has not signed any agreement with unions to represent miners, the sunny promises of good, high-paying jobs start to get murky.

We do not have the space here to discuss Glencore’s dismal environmental record.

The citizens of Northeastern Minnesota are right to advocate for better, higher-paying jobs that allow communities to thrive. The economic well-being of the region is vital to the rest of Minnesota. But we need to see beyond the rosy public-relations materials and promises made by mining companies and take a close look at who will operate the mines.

If Glencore breaks ground, everyone in Minnesota should be concerned.

Chris Knopf of North Oaks, Minn., is executive director of the Friends of the Boundary Waters Wilderness (