Amethyst Geode on Pin StandA cave of violet crystals, mounted and open to the room. Amethyst geodes form when silica rich fluids enter cavities in basaltic rockmost often in the volcanic formations of southern Brazil and Uruguayand deposit quartz crystal slowly from the walls inward. The violet color develops from iron impurities within the quartz lattice, deepening where crystal growth was slowest. This specimen is mounted on a pin stand, which holds it open faced so the druzy