Naica Mine

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Enormous gypsum crystals in a Naica cavern, found during mining. Note person for scale.

The Naica Mine of the Mexican state of Chihuahua, is a working mine that is best known for its extraordinary selenite crystals.[1] Located in Naica in the municipality of Saucillo, the Naica Mine is a lead, zinc and silver mine operated by Industrias Peñoles, Mexico's largest lead producer.[2] Caverns discovered during mining operations contain crystals of selenite (gypsum) as large as 1.2 m (4 ft) in diameter and 15 m (50 ft) long. Peñoles announced in October 2015 that it was indefinitely suspending operations at Naica Mine.[3]

Currently, the high temperature is 58° C (136° F) with 99% humidity, which interferes with breathing and increases the risk of asphyxiation. Because of this, researchers require specialized suits with an oxygen supply to survive working in the environment.

Cave of the Crystals[edit]

Main article: Cave of the Crystals
Location of the Swords and Crystal caves with the gypsum crystals within the idealized block diagram of Naica mine

The Cave of Crystals is a cave approximately 300 m (1,000 ft) below the surface in the limestone host rock of the mine. The chamber contains giant selenite crystals, some of the largest natural crystals ever found.[4][5] The selenite crystals were formed by hydrothermal fluids emanating from the magma chambers below. The cavern was discovered while the miners were drilling through the Naica fault, which they were worried would flood the mine. The caves are closed to the public, and remain closed after a worker tried to enter the cave to steal some of the selenite, only to suffocate and die in the cave's humid and inhospitable atmosphere.[6] After enough research on the crystals has been carried out, some of the chambers will be allowed to flood again and continue the process of crystal growth.

The Cave of Swords[edit]

The Cave of Swords is another chamber in the Naica Mine, also containing gypsum crystals but each "only" about a meter long, due to the fact that these crystals are younger and had been growing for much less time by the time they were discovered.[5]


Crystals from the Naica mine
Selenite crystals from Naica mine. Scale unknown. 
Green fluorite framed by white calcite, Naica Mine, mined in the 1980s. Size: 5.5 cm × 5.1 cm × 4.4 cm (2 14 in × 2 in × 1 34 in). 
Sphalerite and galena ore specimen from the Naica mine. Size: 4.7 cm × 3.6 cm × 2.6 cm (1 34 in × 1 12 in × 1 in). 

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Coordinates: 27°51′3″N 105°29′47″W / 27.85083°N 105.49639°W / 27.85083; -105.49639