The rocks that Molycorp pulls from the earth at its Mountain Pass, Calif., mine move to a crushing facility nearby. There, the ore gets pounded into pieces about three-eighths of an inch wide. Those pebbles then move via conveyer belt to a mill, get mixed with water and dumped into a giant cylinder with large steel balls that turn the mixture into a slurry. Then Molycorp adds chemicals and heats the slurry up. The rare-earth minerals rise with the bubbles that float to the top and are skimmed off.