Mysterious Cave Houses World's Largest Crystals

Tucked away in the Mexican desert, hiding in the depths of a mysterious mountain called Naica, is a breathtaking cavern carved by the world's largest crystals. An elite team of scientists journeyed 1,000 feet underground to reveal the world's latest natural wonder and unlock the mystery of how these megalith marvels came to exist.

"In a sense, we're looking for clues at the scene of a crime, and the crime occurred three and a half billion years ago," said Chris McKay, a NASA Ames Research Scientist.

The secret of the crystal cave was first unlocked in 2000 by Mexican brothers Eloy and Javier Delgado while they were mining for lead.

Eloy Delgado recalls the moment he set foot into the cave and witnessed the crystals firsthand. "I went in, I shined the light on it, and it reflected everywhere. How cool!"

Research dates the birth of the crystals back half a million years, when the hot magma from the Earth's core that created Naica also filled its caves with scalding water for many millennia. The combination of water and heat allowed a mineral called gypsum to slowly collect along the cave walls, gradually creating the gigantic crystals.

Filled with razor-sharp gems the size of telephone poles, reaching 35 feet in length and weighing in at 60 tons apiece, the cave resembles a massive geological playground for the enthusiastic scientists.

"It's hard to focus on a particular crystal -- there are so many vying for your attention," McKay said. "If I wasn't seeing it, I wouldn't believe that it could exist."

But with temperatures above 113 degrees Fahrenheit and crystal edges that can slice through human flesh, the cave poses great danger to its human visitors. Due to the high temperatures, the human body must sweat to cool itself, but the 100 percent humidity makes it impossible to sweat. In turn, cells die and organs could overheat and fail, one by one.

The great risk involved is not enough to deter the scientists, who must don ice suits and respirators with chilled air in order to survive longer than five minutes inside the cave. Their vital signs are closely monitored throughout.

"The cave here provides two bits of information with respect to the search of life," McKay said. "One is it tells us about life at high temperatures. That's interesting. But even more interesting, it tells us about how evidence of life is preserved over a long period of time, over geological time."

Despite their incredible sense of glory and amazement, the scientists realize the crystal cave will not live on indefinitely. Now that the crystals are exposed to less heat and no water, they are slowly but surely eroding away. In the meantime, however, the lessons that this crystal cave can provide are invaluable.

"By investigating the life in these environments, I think we expand our understanding of the limits to life," McKay said. "For us in planetary science, that understanding of the limits of life is the basis of our search. When you say, 'What are we going to look for?' Well, we're going to look for life."

"Giant Crystal Cave" premieres Sunday at 9 p.m. on the National Geographic Channel.