Gypsum
Image: Alexander Van Driessche (CC BY 3.0)
Mineral NameGypsum
Chemical FormulaCaSO₄·2H₂O
Mohs Hardness2
Crystal Systemmonoclinic
Streak Colorwhite
Cleavageperfect in one direction, good in another, imperfect in a third
Fractureconchoidal to uneven
Specific Gravity2.32
Colorscolorless, white, pale blue
Transparencytransparent to translucent
Type LocalityNaica Mine, Chihuahua, Mexico
Mineral GroupSulfates
Usesscientific study, collector specimens, plaster of Paris, drywall, fertilizer
Associated Mineralsanhydrite, calcite, sulfur
Raritylegendary
Description
The image displays a breathtaking view of enormous, translucent, prismatic gypsum crystals, some several meters long, forming an intricate lattice within the Naica Cave, with a person providing scale to their immense size. The crystals appear pale white to light blue, reflecting light from within the cavern.
Geological Context
These colossal gypsum crystals formed in a hydrothermal environment within a limestone cave, where hot, sulfate-rich waters slowly cooled over hundreds of thousands of years, allowing the calcium sulfate to precipitate and grow into these extraordinary sizes. The Naica mine is known for its lead, zinc, and silver deposits, and the caves are a byproduct of the same geological processes.
