It is an EXTREMELY dangerous cave because of extreme temperatures that are deadly to humans.
Here are a few facts concerning this marvel of nature. Hidden deep beneath the surface of the Earth is one of the greatest natural marvels on the planet: a giant crystal cave with crystals up to 36 feet long and weighing 55 tons. But this scorching cavern could kill humans after just 15 minutes of exposure.
The giant crystals found in the caves at Naica are softer than a human fingernail.
The largest crystal found at Naica is 500,000 years old.
The stunning crystal pillars are made from the same common mineral as drywall – it's called gypsum.
The Naica cave's deadly heat comes from the depths of the Earth. Naica sits on a set of fault lines. A magma chamber a mile and a half down warms the water that flows throughout the mountain.
The Naica principle cave "Cueva de Los Cristales" is 113°F and 100% humidity.
The water pumped from the Naica mine formed a lake in the arid Chihuahua desert and is also used to irrigate a golf course.
Naica is one of the most productive lead mines in the world, and a huge supplier of the world's silver as well.
The Naica cave actuality footage was shot on solid-state memory HD video cameras (tape-less) wrapped in plastic bags and pre-heated for three hours prior to entering the cave.
The Naica Project team created a stop-motion robot and fitted it with a Nikon digital still camera powered by a custom software to capture beauty-shot sequences of the cave with 10-megapixel resolution.