Giant Gypsum Rosette
Wearing an ice-pack vest, Mario Corsalini stands by a giant rosette of gypsum in the Naica Mine's crystal cavern.
A multifaceted "butterfly" crystal clings to the wall in the Naica Mine's Cave of Crystals. These crystals formed in mineral-rich water heated to right around 136 degrees F (58 degrees C), a temperature at which the mineral anhydrite in the water is deposited as gypsum, according to 2007 research in the journal Geology. The gypsum in the crystals is in the form of selenite.
Experiencing the Cave
Laura Rosales Lagarde of the University of Nevada, Las Vegas, takes a moment to experience the heat of the Cave of Crystals without an ice suit or other protective gear. With temperatures that can hover near 140 degrees F (60 degrees C), the cave is tolerable for an unsuited person for just a few moments.