Last Fall, adventurer and filmmaker George Kourounis traveled to Naica to see the incredible "Crystal Cave of Giants" for himself. Though there's little risk of eruption from the nearby magma chamber, the cave itself is still deadly hot – over 120 Fahrenheit with about 90 percent humidity. People are only allowed in without cooling suits for a few minutes at a time.
Kourounis detailed his journey on his Web site:
"When we first arrived at the Naica mine, Manuel and his crew took us inside without wearing the special cooling suits. This was in order to get us used to what REAL heat is like. There is a steel door protecting the cave and as soon as you pass through it, the temperature hits you like a truck.
But as soon as you get your first glimpse of the incredible crystals, you want to keep going deeper. We were inside for only 14 minutes, which was pushing the danger limits without cooling suits. When we exited, the staging area was a "cool" 41 Celsius. My heart was pounding and I was completely soaked in sweat, my shirts, pants, socks & boots... Everything. All we could do was sit, drink and rest."
Cooling suits - vests of frozen gel packs surrounded by insulation, plus a backpack that supplies the wearer with chilled air to breathe - allow people to remain in the mine for close to an hour. Kourounis and his crew took the opportunity to snap these incredible images as well as shoot some video.
Of his experience visiting the crystal cave, Kourounis writes:
"I've never seen such a spectacular place. It was like setting foot on a new planet. Many of the crystals were so large that I couldn't even wrap my arms around them and the terrain was so difficult to walk on that we had to be extremely cautious not to slip and fall. Doing so would could get you impaled on a sharp crystal and would require a dangerous and difficult rescue."
Sadly, once the silver in Naica runs out, miners will likely turn the pumps off again. The chamber will fill with water, the crystals will once again be among Earth's vast, inaccessible depths.