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.

Geodes are hollow rock formations often with quartz crystals, such as amethyst, inside. Amethyst geodes in Uruguay have been found in cooled lava flows, which date from the original breakup of the ...