Cave of Giant Crystals
The Cave of the Crystals or Giant Crystal Cave is a cave connected to the Naica Mine 980 ft below the surface in Naica, Chihuahua, Mexico – about 200 miles south of Presidio. The main chamber contains giant selenite crystals (gypsum, CaSO4·2 H2O), some of the largest natural crystals ever found. The cave’s largest crystal found to date is 39 ft in length, 13 ft in diameter and 55 tons in weight. The cave is extremely hot with air temperatures reaching up to 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. A group of scientists known as the Naica Project have been heavily involved in researching these caverns. No public tours are available.
Naica Project (http://www.naica.com.mx/english/index.htm), comprehensive website on the Crystal Caves with geology, history, photos and videos
BBC page on the cave with video (http://news.bbc.co.uk/1/hi/sci/tech/8466493.stm)
Discovery of the largest crystals on Earth (http://www.canyonsworldwide.com/crystals/mainframe3.html) by Richard D. Fisher
Naica Crystal Caves (http://www.showcaves.com/english/mx/caves/Naica.html) at Caves of Mexico
Giant Crystal project (http://giantcrystals.strahlen.org/america/naica.htm)
Crystal Cave of Giants (http://www.stormchaser.ca/Caves/Naica/Naica.html), account of a 2009 visit by George Kourounis