Commentary:
These amazing images circulate via email and are also a popular topic for blog and online message board posts. According to the description that accompanies the images, they depict a cave of giant crystals found deep in the ground at a mine in Mexico. This description is accurate and the photographs are genuine.
The Cave of Crystals (Cueva de los Cristales) was discovered in 2000 by miners at the Naica Mine in the Mexican state of Chihuahua.
In April 2000, brothers Juan and Pedro Sanchez were drilling a new tunnel when they made a truly spectacular discovery. While Naica miners are accustomed to finding crystals, Juan and Pedro were absolutely amazed by the cavern that they found. The brothers immediately informed the engineer in charge, Roberto Gonzalez. Ing. Gonzalez realized that they had discovered a natural treasure and quickly rerouted the tunnel.
The cave contains some of the largest natural crystals ever discovered. The cavern was originally filled with water, but was pumped clear during mining excavations. The mining company's pumping operations continue to keep the cave clear of water. Temperatures in the cave are consistently very high, and humans can only spend a few minutes inside before the heat becomes overwhelming. According to a National Geographic article about the cave, it was because of this stable high temperature and mineral rich water that the crystals were able to grow so unusually large:
To learn how the crystals grew to such gigantic sizes, García-Ruiz [of the University of Granada in Spain] studied tiny pockets of fluid trapped inside.
The crystals, he said, thrived because they were submerged in mineral-rich water with a very narrow, stable temperature range—around 136 degrees Fahrenheit (58 degrees Celsius).
At this temperature the mineral anhydrite, which was abundant in the water, dissolved into gypsum, a soft mineral that can take the form of the crystals in the Naica cave.
The crystals would have taken many hundreds of thousands of years to reach such gigantic proportions.
Another crystal-filled cave, dubbed the Cave of Swords, was discovered at the Naica Mine in 1910. This cave is located much closer to the surface than the later discovery and its crystals are considerably smaller. Professor García-Ruiz notes that there may well be undiscovered caves at the site that also contain very large crystals.
Access to the cave is currently restricted in order to preserve the crystals as much as possible. If mining in the area eventually stops, pumping may also stop and the cave will then refill with water, allowing the crystals to start growing once again. Or perhaps arrangements can be made to continue pumping even if the mine closes so that the cave will remain accessible for humans to enjoy. Thus, the long-term future of this amazing place remains somewhat uncertain.