<Tr> <Th> Hazards </Th> <Td> High temperature and humidity </Td> </Tr> <Tr> <Th> Access </Th> <Td> Restricted </Td> </Tr> <P> Cave of the Crystals or Giant Crystal Cave (Spanish: Cueva de los Cristales) is a cave connected to the Naica Mine at a depth of 300 metres (980 ft), in Naica, Chihuahua, Mexico . </P> <P> The main chamber contains giant selenite crystals (gypsum, CaSO 2 H O), some of the largest natural crystals ever found . The cave's largest crystal found to date is 12 m (39 ft) in length, 4 m (13 ft) in diameter and 55 tons in weight . The cave is extremely hot, with air temperatures reaching up to 58 ° C (136 ° F) with 90 to 99 percent humidity . The cave is relatively unexplored due to these factors . Without proper protection, people can only endure approximately ten minutes of exposure at a time . </P>

Where is the naica cave of crystals located