Asarco's open-pit Ray Mine in Arizona is so rich in copper that water sprayed on its dirt roads to keep down the dust instantly turns green as the ore oxidizes. If you stand at the bottom of the mine, which covers more than 50,000 acres, and look up at its high, tiered walls, you travel back in time to the top shelf, where the first cuts were made a generation ago by men with picks and shovels. Here at the bottom, though, the world's largest wheel loader--the LeTourneau L-2350--gulps 75 tons in a single bite.
