Here is more information on what Marty showed us. EL-777
http://www.showcaves.com/english/mx/caves/Naica.htmlCAVE OF THE CRYSTALS - The world's largest known crystals
Location: Naica Hills, south of Chihuahua City.
Description
The word Naica is of Tarahumara origin and means shady place. It was given to the hills, maybe because of a spring with some trees. The hills are full of minerals which made them valuable for mining. The mine produces lead, zinc, copper, silver and gold and is one of the most productive mines in Chihuahua.
In the last years the care of the environment and for minimum contamination by the present mining comany gave the mine a national level of prominence. Hopefully this attitude amongst the miners may also protected the Cave of the Crystals.
This mine is not a show mine, but a still working and producing mine. It is very hot and has a huge underground well of 52°C hot water. The air of the mine is cooled down by a ventilation system to about 40°C, but the humidity of the air is about 100%. The topic of this page is not the mine, but two natural caverns found inside the mine.
The Cueva de las Espadas (Cave of Swords) was found in 1910 and contains extraordinary large selenite (gypsum) crystals. It is named after the crystals, which resemble swords. The natural cave is a single huge chamber about 70m in diameter and 120m below surface. The prismatic gypsum crystals, which are called selenite, are up to 2m long and 25cm in diameter. The Cave of Swords is famous among geoscientists and visited very often, thus it is equipped with paths, light and ventilation. Unfortunately the habit of removing crystals for the mineralogical museums of the world deprived the cave of its best pieces. The change in the cave climate further damaged the crystals and made them dusty and opaque.
The newest discovery is the Cueva de los Cristales (Cave of the Crystals), even more spectacular than the Cave of Swords. At a depth of 300m first a spherical chamber of 8m diameters filled with selenite crystals was found. The tunnel was rerouted, but soon after a second, even bigger chamber with several big selenite crystals, 8m long and 2m in diameter, was found. The longest crystal is 11m long. It was closed by a brick wall and an iron gate to protect the crystalls.
As the temperature inside the cave is 60°C and the humidity 100%, a visit of the cave always includes a perfect steam bath. But for work in the cave it is really problematic. First it was absolutely impossible to take any picture of the cave as cameras first steamed up, and when they reached the temperature of the cavern, the electronic was dead. The researchers developed special techniques for the temperature, but more than 10 minutes are not possible inside the cave. Typically two or three minute visits are applicable.
A mine worker who tried to steal some crystals died in the cave: the temperature and the bad air causes dehydration and after a few minutes he was too weak to leave the cave and suffocated. When he was found, his body was cooked (well done to be exact).
The exploration is done by La Venta, an Italian group of cave explorers, and a Méxican company named Speleoresearch & Films. They have an agreement with the mining company Industrias Peñoles about the protection of the cave. The technical difficulties of the exploration are immense, and so far the total size of the cave is still unknown, as it is impossible to explore more than a few tens of meters in the available time. Special breathing and protection systems are developed with the goal to stay inside the cave for at least one hour.
The formation of the large selenite crystals was explored during the last years by Juan Manuel Garcia-Ruiz from the University of Granada in Spain and others. The results were published in the April 2007 issue of the journal Geology of the Geological Society of America. They determined the exact conditions of the crystal growth by analyzing the water contained in tiny pockets inside the crystals. They grew in gypsum rich water at about 58°C, heated by the volcanic activities below.
See also
Crystal Moonbeams by John F. Ross, Smithsonian Magazine
Las Cuevas de Naica, The Naica Caves, the homepage of Speleoresearch & Films, with extraordinary pictures and in detail information.
Cave of the "Crystal Giants": New Discovery of the World's Largest Known Crystals
Crystal Moonbeams by John F. Ross, in Smithsonian, April 2002.
NAICA, Cueva de los Cristales, Cave of the Crystals, in the Naica-Peñoles mine, cave of largest selenite (gypsum) crystals in Naica | La Venta Exploring Team
GSA Journals Online - Journal -
AmbergrisCaye.com 
