http://www.odditycentral.com/pics/the-crystal-cave-of-giants.html#more-1251 This is where you have to go if you want to see the biggest crystals on the planet. Found in Naica mine of Chihuahua, Mexico, the Crystal Cave of Giants is a chamber hosting some of the most amazing crystals you’ve ever seen. They look like silver or golden giants, and reach 11 meters in length, 1.5-2 meters in diameter and 55 tons in weight. Until 2007, the reason for their abnormal size was unknown, but now it’s clear it has something to do with mineral rich water the crystals bathed in for millions of years and the constant temperature that never drops bellow 150 degrees Fahrenheit. Ever since it was uncovered, The Crystal Cave of Giants has sustained considerable giant from the outside world, so the mining company operating in the mine has installed iron doors to seal off access. http://news.nationalgeographic.com/news/2007/04/photogalleries/giant-crystals-cave/ April 9, 2007—Geologist Juan Manuel García-Ruiz calls it "the Sistine Chapel of crystals," but Superman could call it home. A sort of south-of-the-border Fortress of Solitude, Mexico's Cueva de los Cristales (Cave of Crystals) contains some of the world's largest known natural crystals—translucent beams of gypsum as long as 36 feet (11 meters). How did the crystals reach such superheroic proportions? In the new issue of the journal Geology, García-Ruiz reports that for millennia the crystals thrived in the cave's extremely rare and stable natural environment. Temperatures hovered consistently around a steamy 136 degrees Fahrenheit (58 degrees Celsius), and the cave was filled with mineral-rich water that drove the crystals' growth. Modern-day mining operations exposed the natural wonder by pumping water out of the 30-by-90-foot (10-by-30-meter) cave, which was found in 2000 near the town of Delicias (Chihuahua state map). Now García-Ruiz is advising the mining company to preserve the caves. "There is no other place on the planet," García-Ruiz said, "where the mineral world reveals itself in such beauty." http://news.bbc.co.uk/2/hi/science/nature/6518161.stm Giant crystals enjoyed perfection The cave was discovered in 2000 Enlarge Image With lengths over 11 meters (36 feet), the giant gypsum crystals found in Mexico's Cueva de los Cristales are a great natural wonder. Now, a Spanish-Mexican team thinks it can explain how these marvels acquired their immense size.

The scientists studied tiny pockets of fluid trapped in the crystals and conducted back-up lab experiments. They report in the journal Geology that the solution from which the crystals grew must have been kept in a very narrow, stable temperature range.

The researchers' analysis leads them to believe there are other dramatic caves waiting to be discovered in the Naica mine complex south-east of Chihuahua city.

"If the theory we propose for the 'genetic' mechanisms of the crystals is right, then I would not be surprised if miners find more of these caves in the next few years," Juan Manuel Garcia-Ruiz, from the University of Granada, Spain, told BBC News. And, in fact, one other has already been found.

Already two remarkable caves are known at Naica, which has yielded some of the world's most significant deposits of silver and lead.

The 120 meter (394 feet) deep Cueva de las Espadas (Cave of Swords), discovered in 1912, is named for its metre-long shafts of gypsum (a calcium sulphate mineral that incorporates water molecules into its chemical formula).

And although individually there are fewer crystals in the 290 meter (951 feet) deep Cueva de los Cristales, its beams are considerably bigger.

Professor Garcia-Ruiz and colleagues believe they can now show how these differences emerged.

The team studied tiny fluid samples embedded inside the crystals themselves. These watery inclusions record tell-tale chemical details of the saline and temperature conditions of the saturated solution from which the mammoth structures developed.

Both caves owe their origin to the volcanism which laid down the metal sulphides - the ores - that have proved so valuable.

Copious amounts of calcium sulphate would also have been created towards the end of this mineralisation process more than 20 million years ago - but in the hot fluids that infused the cracks and cavities in the rock, this calcium sulphate would have taken the form of anhydrite. Anhydrite has the same chemical formula as gypsum, except that it excludes water. Only as the magma chamber deep under the Naica mountain cooled did the hot fluids above start to fall to a temperature at which anhydrite could switch to gypsum. Professor Garcia-Ruiz and colleagues say their studies indicate that the deeper of the two caves - Cueva de los Cristales - must have been kept just below the transition temperature for many hundreds of thousands of years. "The conditions were perfect. By maintaining the temperature just below 58 degrees for a very long time you get a few, very big crystals," said Professor Garcia-Ruiz. "You can see that many areas on the cave's walls are empty; they have no crystals. The walls are red because of the iron oxide. The reason we know this happened for many years is because we studied the fluid inclusions inside the crystals." It is likely the upper cave - Cueva de las Espadas - fell below the transition temperature much more rapidly and consequently grew many, smaller crystals. Heritage future? The particular crystalline form taken by the gypsum is selenite which is known for its translucency. Their future will be dependent on the fate of the mine. At the moment, access is restricted to prevent damage to the soft crystals. And humans can only get in the caves at all because of the continuous pumping operations that keep them clear of water. If, when Naica's ores are no longer viable, the mine is closed and the pumping is stopped, then the caves will be submerged - and the crystals will start growing again. "I've recommended to the mining company that they try to preserve them and I would like to see Unesco get involved," explained Professor Garcia-Ruiz. "Later on we should decide whether to keep them available for people to visit and enjoy, or let the natural scenario return." http://en.wikipedia.org/wiki/Selenite Wikipedia CaSO4·2H2O http://www.crystalinks.com/mexicocrystals.html The Naica Mine of Chihuahua, Mexico, is a working mine that is known for its extraordinary crystals. Naica is a lead, zinc and silver mine in which large voids have been found, containing crystals of selenite (gypsum) as large as 4 feet in diameter and 50 feet long. The chamber holding these crystals is known as the Crystal Cave of Giants, and is approximately 1000 feet down in the limestone host rock of the mine. The crystals were formed by hydrothermal fluids emanating from the magma chambers below. The cavern was discovered while the miners were drilling through the Naica fault, which they were worried would flood the mine. The Cave of Swords is another chamber in the Naica Mine, containing similar large crystals. The Naica mine was first discovered by early prospectors in 1794 south of Chihuahua City. They struck a vein of silver at the base of a range of hills called Naica by the Tarahumara Indians. The origin in the Tarahumara language seems to mean "a shady place". Perhaps here in the small canyon there was a grove of trees tucked away by a small canyon spring. From that discovery, until around 1900, the primary interest was silver and gold. Around 1900 large-scale mining began as zinc and lead became more valuable. During the Mexican Revolution the mine was producing a great deal of wealth. Revolutionary troops entered the town and demanded money from the owners. One of them was assassinated when he refused to pay, causing the mine to shut down from 1911 to 1922. Just before the mine was closed, the famous Cave of Swords was discovered at a depth of 400 feet. Due to the incredible crystals, it was decided to try to preserve this cave. While many of the crystals have been collected, this is still a fascinating cave to visit. In one part there are so many crystals on one of the walls, they appear to be like an underwater reef moving in a gentle undulating motion in an ocean current. In April 2000, brothers Juan and Pedro Sanchez were drilling a new tunnel when they made a truly spectacular discovery. While Naica miners are accustomed to finding crystals, Juan and Pedro were absolutely amazed by the cavern that they found. The brothers immediately informed the engineer in charge, Roberto Gonzalez. Ing. Gonzalez realized that they had discovered a natural treasure and quickly rerouted the tunnel. During this phase some damage was done as several miners tried to remove pieces of the mega-crystals, so the mining company soon installed an iron door to protect the find. Later, one of the workers, with the intention of stealing crystals, managed to get in through a narrow hole. He tried to take some plastic bags filled with fresh air inside, but the strategy didn't work. He lost consciousness and later was found thoroughly baked. When entering the cave our group is issued helmets, lanterns, rubber boots, and gloves. One must then be driven by truck into the main mining tunnel called Rampa Sn. Francisco. While the vertical drop is approximately 1000 feet, the drive is almost a half mile long. The heat steadily increases and women have been observed to begin "glowing". The truck stops in front of a concrete wall with a steel door. The intense heat can prevent brain functioning. At the end of the tunnel there are three or four steps into the aperture of the cavern itself. It is in this short tunnel. In this short distance the temperature and humidity goes from being uncomfortably warm to literally a blast furnace. Momentarily, the penetrating heat is forgotten as the crystals pop into view on the other side of the "Eye of the Queen". The entire panorama is now lighted and the cavern has a depth and impressive cathedral-like appearance that was not visible on earlier trips with just our headlamps. When inside the great cathedral of crystals, the pressure of intense heat create a gamut of emotions and perhaps hallucinations. One can only remain for a short period of time. Geologists report that these natural crystal formations are incredibly complex, yet so simple. They have a magical or metaphysical personality independent of their chemical structures. There is a magma chamber two to three miles below the mountain and that heat from this compressed lava travels through the faults up into the area of the mine. Super heated fluids carry the minerals the miners are seeking as well as form the crystals. The mine is ventilated; otherwise, it could not be worked. Some parts, however, are not air-conditioned, such as the Cave of the Crystals, and there you feel the heat from the magma deep below. The fluids travel along the Naica fault, enter voids in the bedrock, and then form entirely natural structures that are not easily explained scientifically. In April 2000, the mining company became confident that the water table on the other side of the fault had been lowered sufficiently to drill. When they did this, it is almost as if a magical veil of reality was breached and an entirely new world was discovered. Two caverns filled with the Earth's largest crystals were immediately revealed. More discoveries are expected to be made in this magical kingdom of intense natural beauty. Selenite, the gypsum crystal, named after the Greek goddess of the moon, Selene, due to its soft white light, is said to have many metaphysical and healing benefits. Selenite powder has been used cosmetically for thousands of years to enhance one's natural beauty. It is believed that this crystal assists with mental focus, growth, luck, immunity, and soothes the emotions.