- Cave of Crystals
- Mexico ()
The Cave of Crystals, below Naica mountain in the Chihuahuan Desert, Mexico, was first discovered in 2000. It contains translucent single crystals of gypsum – the largest of which measure about 11 m long and weigh an estimated 55 tonnes. The cave itself is around 30 m long and horseshoe shaped. The giant crystals formed when the cave was filled with warm mineral rich water and the largest have taken many hundreds of thousands of years to reach their current sizes.