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9 jaw-dropping caves

By: Catie Leary on June 11, 2010, 1:05 p.m.
Cave of the Crystals

Photo: Courtesy of Carsten Peter/National Geographic

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Cave of the Crystals

The discovery of the Cave of the Crystals in 2000 by miners working 1,000 feet underground proved that there are still astounding natural wonders that humans have yet to stumble upon. Located in the Naica Mine near Chihuahua, Mexico, the cave features enormous crystalline blocks and beams jutting out from all directions. The selenite crystals — some of the largest ever found — formed when the cave, situated along an ancient fault, filled with hot, mineral-rich water. The water remained in the cave for about 500,000 years, providing an ideal climate for the giant crystals to grow.