PolyMet Mining Corp., the company out to start what is expected to become a wave of copper, nickel and other precious mineral mining operations in northern Minnesota, is facing new pressures beyond environmentalists who get most of the news attention in the state. Copper prices remain low as worldwide production continues to outpace demand. Prices are lower than they were 10 years ago.

Helping it, however, is the fact that its largest investor has the ability to sway worldwide copper prices.

Glencore PLC, one of the world’s largest mining businesses, owns one-third of PolyMet’s stock. Yesterday, it announced it will close one of its largest copper and cobalt mines by the end of the year (located in the Congo), according to the Wall Street Journal. The move is expected to reduce worldwide cobalt output by 20 percent, and copper output by less than 1 percent. Three years ago, Glencore temporarily suspended mining operations at its majority owned Katanga Mining Ltd. in the Congo, and that move caused copper prices to shoot upward.

Ten years in the making, PolyMet’s billion-dollar-plan for northern Minnesota continue to be met with a barrage of legal efforts by environmentalists to kill the project. They cite concerns that copper-nickel mining’s toxic waste water may leak beyond containment ponds and seep into the waterways that flow into the Boundary Waters Canoe Area Wilderness.

Earlier this week, their concerns convinced the Minnesota Court of Appeals to place a hold on a state-issued water quality permit needed for PolyMet’s mining operation to move forward, pending a review of “irregularities” during the permitting process.