Cave of the Crystals

Cave of the Crystals or Giant Crystal Cave is a cave connected to the Naica Mine at a depth of 300 metres, in Naica, Chihuahua, Mexico. It takes the form of a chamber within the limestone host rock of the mine, and is about 109 metres long with a volume of 5,000 to 6,000 cubic metres.

The chamber contains giant selenite crystals, some of the largest natural crystals ever found. The largest is 11.40 metres, with a volume of about 5 cubic metres, and an estimated mass of 12 tonnes. When not flooded, the cave is extremely hot, with air temperatures reaching up to 58 °C with 90 to 99 percent humidity. This is comparable to temperature records in Death Valley, but with much wetter air that results in a much higher wet bulb temperature; this prevents cooling via sweating. The cave is relatively unexplored because of these factors. Without proper protection, people can only endure approximately ten minutes of exposure at a time.