http://www.unitedyam.com/golb/wonderland-places-the-cave-of-the-crystals/ - Cave of the Crystals or Giant Crystal Cave – Spanish: Cueva de los Cristales – is a cave connected to the Naica Mine 980 ft below the surface in Naica, Chihuahua, Mexico. The main chamber contains giant selenite crystals (gypsum, CaSO4·2 H2O), some of the largest natural crystals ever found.
The Naica Mine of the Mexican state of Chihuahua is a working mine that is best known for its extraordinary selenite crystals. ナイカ鉱山 チリ
"The Sistine Chapel of crystals" ~ Naica, Chihuahua, Mexico's 'Cueva de los Cristales' (Cave of Crystals) contains some of the world's largest known natural crystals—translucent beams of gypsum as long as 36 feet. "There is no other place on the planet where the mineral world reveals itself in such beauty." Unfortunately, the gypsum started to deteriorate when the cavern was drained of water, and it had to be re-flooded. This will never be seen again.