Cave of the Crystals or Giant Crystal Cave is a cave in Naica, Chihuahua, Mexico.
The cave was discovered in April 2000 by miners excavating a new tunnel for the Industrias Peñoles mining company located in Naica.
Cave of the Crystals is connected to the Naica Mine at a depth of 300 meters (980 feet).
The main chamber contains giant selenite crystals, some of the largest natural crystals ever found.
The cave’s largest crystal found to date is 12 meters (39 feet) in length, 4 meters (13 feet) in diameter and 55 tons in weight.
Cave of the Crystals is a natural marvel but is rarely accessible because of the conditions. When it was accessible, the cave was extremely hot, with air temperatures reaching up to 58 °C (136 °F) with 90 to 99 percent humidity.
The cave is relatively unexplored due to these factors. Without proper protection, people could only endure approximately ten minutes of exposure at a time.
To learn how the crystals grew to such gigantic sizes, scientist Juan Manuel García- Ruiz 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 58 °C (136 °F). 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 this cave.
The cave itself lies above an underground magma chamber, which heated groundwater to levels where it was saturated with minerals.
Using uranium dating, scientists were able to determine that the crystals were 500,000 years old.
In early 2017, researchers reported finding dormant microbes inside the crystals. They had probably been trapped inside the crystals at least 10,000 years ago and possibly as long as 50,000 years ago. Some bacteria living in the cave do not match any other known life forms on the planet.
The cave was featured on the Discovery Channel program Naica: Beyond The Crystal Cave in February 2011. Exploration has given credence to the existence of further chambers, but further exploration would have required significant removal of the crystals. As the cave’s accessibility is dependent on the mine’s water pumps, when mineral exploitation is ended in the area it was likely pumping would stop and water level allowed to rise again.
In February 2017, Penelope Boston reported to the BBC that mining operations had ceased and that the cave have re-flooded.