CRYSTAL PARK, Mont. — Molten granite formed the Pioneer Mountain Range in southwest Montana about 72-million years ago. As the granite cooled, water carried quartz and other minerals through the rocks ...

Moonstones in Montana, amethyst and emeralds in North Carolina, garnet and quartz in upstate New York. At pay-to-dig mines around the United States, visitors can paw through piles of mine tailings to ...