ST. PAUL, Minn. – The state Supreme Court affirmed a lower court’s reversal of a mining permit for the proposed PolyMet copper-nickel mine on Minnesota’s Iron Range. The Court said the state Department of Natural Resources should have set a fixed period for the permit to mine, rather than leaving it open-ended. The decision is the latest setback for the $1 billion PolyMet project but not necessarily the final word. The Court said the Natural Resources Department may choose to conduct adversarial hearings to gather more evidence on whether a bentonite clay lining for the mine’s waste basin can contain acidic mine tailings. . The justices said it found no convincing evidence in the record that pollution can be contained.