Amethyst is one of the most abundant crystals in the world. But the most prized pieces can cost almost a million dollars. Some of the world's largest amethyst geodes come out of Artigas, Uruguay. The earth beneath this region is uniquely suited to producing amethyst. But other than size, what qualities do miners look for in a valuable amethyst? And how are the crystals prepared once they're out of the ground? We explored why amethyst geodes are so expensive.