Cave of Crystals

Cave of Crystals, Naica: The World’s Largest Crystals You Cannot Currently Visit

The Cave of Crystals beneath the Naica mine in Chihuahua, Mexico, was discovered in 2000 when miners drilling a new tunnel broke through the chamber ceiling. Inside were selenite crystals up to 11 metres long and over a metre in diameter, the largest natural crystals ever found. The cave temperature is approximately 58°C with near-100% humidity; without refrigerated suits, a human being loses consciousness in about 10 minutes. Researchers who studied the cave wore ice-pack suits that bought them roughly 30-minute windows inside.

In 2017, the mining company that operates the Naica mine flooded the mine’s lower levels as part of dewatering operations. The Cave of Crystals is currently submerged and inaccessible. It is unclear when or whether it will be accessible again.

Why It Matters

The crystals formed over approximately 500,000 years in a geologically stable environment: hydrothermal waters rich in calcium sulphate saturated the cavern, and the stable temperature of around 58°C allowed the anhydrite in the water to slowly convert to gypsum, growing crystal by crystal at a rate too slow to see in human lifetimes. When the mine was dewatered in the 20th century and the cave discovered in 2000, the removal of water from the environment began slowly deteriorating the crystals. Even during the brief period of scientific access, researchers were watching a millennia-long process begin its reversal.

The cave is among the most extreme examples of biomineralogy: scientists found living organisms, microbial communities, trapped in fluid inclusions inside the crystals, dormant for as long as 50,000 years and revivable in laboratory conditions. This has implications for astrobiology, the search for life in similar extreme environments on other planets.

What You Can Do

Visiting the closed cave is not possible. What is possible is visiting Chihuahua City, which serves as the regional hub, and from there the Naica area.

Chihuahua City has the Museo Casa Chihuahua and the Palacio de Gobierno with murals depicting the region’s history, including the execution of Miguel Hidalgo (whose severed head was displayed on the Alhóndiga in Guanajuato in 1811). The city is also the starting point for the Copper Canyon (Barrancas del Cobre) railway journey, which rivals the Trans-Siberian in scenery and in operational complexity: the Ferrochihuahua route from Chihuahua to Los Mochis descends from 2,400 metres to sea level through a series of gorges deeper than the Grand Canyon.

The Naica mine region itself offers little for visitors beyond the geological significance. For the crystals themselves, the Natural History Museum in London has a substantial collection of selenite specimens and documentation of the cave discovery.

Practical Notes

Naica is approximately 200km southeast of Chihuahua City by road, a 2-3 hour drive through Chihuahuan desert. There is limited accommodation in Saucillo, the nearest town. For anyone making the journey, the town of Chihuahua is the practical overnight base. Airlines connect Chihuahua City to Mexico City, Guadalajara, and several US cities including Dallas.