An excerpt from the Angry Planet TV series featuring the Crystal Cave of Naica, Mexico. www.furiousearth.com
The Crystal Cave of Giants was accidentally discovered in 2000 by miners working in the silver and lead mine at Naica, Mexico. It lies almost 300 meters (900 feet) below the surface of the Earth and it contains the largest crystals known in the world, by far. The largest crystals are over 11 meters long (36 feet) and weigh 55 tons.
The crystals themselves are made of selenite which is crystallized gypsum, the same material used in drywall construction. Except these crystals formed over a span of about half a million years in a hot water solution, saturated with minerals. The the temperature inside the cave remained very consistently hot for the entire time the crystals were growing.
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.
The Suits - The custom designed cooling suits only delay the inevitable. As soon as you enter the cave, you begin to overheat and heat stroke and death are inevitable if you remain inside too long. The suits will extend your stay in the cave but it is up to the individual to recognize when you've been exposed too long. 30-50 minutes is the maximum, depending on the individual.
Each suit consists of several layers of protection. First is an insulated vest which protects you from frostbite which you could get from having ice in direct contact with the skin. Then the ice vest which is a series of gel filled pouches, sewn into a mesh vest and kept frozen. This cools you body's core temperature. Overtop of all that is a set of rugged overalls. These keep the radiant heat from the cave away from the ice plus they protect you from the sharp crystals. Last but not least is the respirator pack. This custom built backpack is made of insulating foam and contains frozen metal ice bottles. A fan blows air over the bottles and it is pumped up a hose to a face mask which is similar to the type worn by fighter pilots. This system allows you to breathe chilled air as long as the ice remains frozen in the pack.
Wearing the suits, you feel like an astronaut that is about to go on a space walk. In reality, it is not all that different, considering the harsh environment.