Naica Mine, The Cave of Giant Crystals, Mexico ~ Incredipedia

The Naica Mine of Chihuahua, Mexico, is a working mine that is known for its extraordinary crystals.
With air temperature of 50C(122F) plus relative humidity of over 90% we get humidex value of 105C (228F) !!! This is one of the most extreme places on the planet.
Naica is a working mine and the only times you can get in is on Sundays and even then only if you know someone working at, or conected to the mines. The days of just suiting up and going in or long gone.

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. 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.

The huge mines at Naica have been excavated for years, but in 1975 a massive area was drained so mining operations could take place. When the water disappeared the crystals stopped growing, however, it was more than 25 years before two miners stumbled across the vast Crystal Caves and the incredible collection of gypsum was discovered. The formation of the beams 290 metres below the surface, occurred when super-heated water began cooling and became saturated with gypsum. Over time, crystals formed in the water. One of the major problems still facing scientists wishing to study below the ground at Naica is the heat. A hot spring located close to the Crystal Caves means the temperature is too hot for people to remain in the crystal chamber for longer than ten minutes at a time.

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.

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.

Ten years after the amazing discovery, scientists are petitioning the Mexican government to claim for Unesco World Heritage status to protect the unique formations for future generations.

It takes 20 minutes to get to the cave entrance by van through a winding mine shaft. A screen drops from the van's ceiling and Michael Jackson videos play, a feature designed to entertain visitors as they descend into darkness and heat. In many caves and mines the temperature remains constant and cool, but the Naica mine gets hotter with depth because it lies above an intrusion of magma about a mile below the surface.
It is still incredibly hot in the cave due its proximity to a magma chamber, deep underground. The air temperature is 50C with a relative humidity of over 90%, making the air feel like an unbearable 105C (228F) Entering the cave without special protective suits can be fatal in 15 minutes. I will be entering the cave wearing a special cooling suit with chilling packs inside and a specialized backpack respirator which will allow me to breath chilled air. Even with all this equipment, I will still only be able to stay in the cave for no more than 45 minutes at a time.
In extreme heat, the body begins to lose higher brain functions which made the expedition much more difficult with the risk of falling into deep pits, or being impaled on a sharp crystal. All the camera gear needs to be slowly brought up to temperature beforehand by pre-heating it and most cameras with moving parts and tape mechanisms simply will not work at all.
It is as dangerous as it is beautiful.

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.