The smokestack for the smelter is just visible in the upper lefthand corner. Gravity is having its way with it and I wouldn't be surprised if it falls down (or is pulled down) over the next few years. When I passed through Superior on my drive to Santa Fe last June, though, it was still standing, so who knows? (I suppose I should drive out there again sometime, but I'm so busy these days...)
FYI, the corrugated tin actually is the back end of the locomotive shed, the building where the mine's freight engine is stored when not in use and also where the maintenance on it is performed.