Giant gypsum crystals grew from a water solution that filled a limestone cave located about 244 m (800 ft) underground in Mexico's state of Chihuahua. In some passageways, the bladelike crystals form a veritable corridor of swords. Miners extending a tunnel in Maravilla Silver Mine accidentally discovered this cave of swords in the early 1900s.
These chisel-shaped crystals grew in a cavity in limestone filled with water rich in dissolved minerals. Large deposits of gypsum are mined to make plaster of Paris, wallboard, alabaster carvings, and stucco.