Caves of giant Selenite crystals formed over 500,000 years, on a fault line over a magma chamber beneath Chihuahua, Mexico. During that time, the caves were submerged in mineral-rich water in which the selenite crystals slowly grew. Some crystals are over 40 feet long. Discovered and drained by miners in 2000, the caves re-flooded in 2017. In the intervening years, scientists captured these images and conducted fascinating mineralogical, crystallographic, biogeochemical, and microbial studies.