The Naica Mine, located in the Mexican state of Chihuahua, is home to some of the world's largest crystals. Discovered in 2000, the mine contains giant selenite crystals, some of which measure up to
From Wikipedia
The Naica Mine of the Mexican state of Chihuahua, is a lead, zinc and silver mine. Located in Naica in the municipality of Saucillo, the Naica Mine is owned by Industrias Peñoles, the world's largest silver producer. Caverns discovered during mining operations contain gigantic crystals of CaSO4 · 2 H2O. Peñoles announced in October 2015 that it was indefinitely suspending operations due to uncontrollable flooding at the Naica Mine.