The Naica Mine of the

Mexican state The states of Mexico are first-level administrative territorial entities of the country of Mexico, which is officially named Mexico, United Mexican States. There are 32 federal entities in Mexico (31 states and the capital, Mexico City, as a sepa ...

Chihuahua Chihuahua may refer to: Places *Chihuahua (state), a Mexican state **Chihuahua (dog), a breed of dog named after the state **Chihuahua cheese, a type of cheese originating in the state **Chihuahua City, the capital city of the state **Chihuahua Mun ...

, is a

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

and

silver Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...

mine Mine, mines, miners or mining may refer to: Extraction or digging * Miner, a person engaged in mining or digging *Mining, extraction of mineral resources from the ground through a mine Grammar *Mine, a first-person English possessive pronoun ...

. Located in

Naica Naica is a town in the Mexican state of Chihuahua. It is located in the municipality of Saucillo. As of 2010, the town of Naica had a population of 4,938, up from 4,775 in the 2005 INEGI Census. It is a mining town and the location of the r ...

in the municipality of Saucillo, the Naica Mine is owned by Industrias Peñoles, the world's largest silver producer. Caverns discovered during mining operations contain gigantic crystals of ( calcium sulfate di

hydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywall. ...

, also sometimes called

selenite Selenite may refer to: Substances containing selenium *A selenium-containing anion or ionic compound with the SeO32− anion: **Selenite (ion), anion is a selenium oxoanion with the chemical formula SeO32− ***Selenous acid, the conjugate acid, w ...

. Peñoles announced in October 2015 that it was indefinitely suspending operations due to uncontrollable flooding at the Naica Mine. The peak underground air temperature was 58° C (136° F) with 100%

relative humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity depe ...

, which rapidly exposed the visitors to

hyperthermia Hyperthermia, also known simply as overheating, is a condition in which an individual's body temperature is elevated beyond normal due to failed thermoregulation. The person's body produces or absorbs more heat than it dissipates. When extreme ...

hazard and caused breathing difficulties. Because of the heat, unprotected researchers could only stay up to 10 minutes inside the cave. Longer visits required the use of a special suit fitted with a cooling system (ice reserve in a backpack with cooled water recirculating in polymer tubes installed over all the body surface) and delivering fresh air for an easier breathing. The visits were limited to about half an hour, the time needed to melt the ice reserves.

Cave of the Crystals

Naica_Ubicación_de_las_cuevas_en_la_mina

The Cave of Crystals is a cave approximately below the surface in the limestone host rock of the mine, about long, with a volume of . The chamber contains giant selenite crystals, some of the largest natural crystals ever found.National Geographic, 2007. Giant Crystal Cave's Mystery Solved
/ref> The largest is , with a volume of about , and an estimated mass of 12 tonnes. The selenite crystals were formed by hydrothermal fluids heated by the

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

chamber below. The cavern was discovered while the miners were drilling through a newly drained area. 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. Reports in 2017 stated that scientists had found "long-dormant microbes" in the crystals and removed them for further research. The cave was closed in 2015 and some of the chambers were allowed to flood again to continue the process of crystal growth. If the mining company decides to open another entrance, researchers might again enter to continue their work, according to a February 2019 report.Naica’s crystal cave captivates chemists
/ref>

The Cave of Swords

The Cave of Swords (''Cueva de Espadas'') is the second-largest chamber in the Naica Mine, at long, with a volume of . It 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 in 1910.

Gallery

References

External links

Naica mine
at

Peñoles Peñoles is a subsidiary company owned by Grupo BAL. Peñoles is the second largest Mexican mining company, the first Mexican producer of gold, zinc and lead and the world leader in silver production. Peñoles is a company with active mines wit ...

Naica Mine
at

Mindat.org Mindat.org is a non-commercial online database, claiming to be the largest mineral database and mineralogy, mineralogical reference website on the Internet. It is used by professional mineralogists, geologists, and amateur mineral collecting, mi ...

Naica Project
comprehensive website on the Crystal Caves with geology, history, photos and videos * * Let's Talk about Crystallization in the Naica Mine, at Wikijunior books for children. {{Coord, 27, 51, 3, N, 105, 29, 47, W, region:MX-CHH_type:landmark_source:wikimapia, display=title Caves of Mexico Lead mines in Mexico Zinc mines in Mexico Silver mines in Mexico Underground mines in Mexico Geography of Chihuahua (state) Landforms of Chihuahua (state) pl:Kryształowa Jaskinia w Naica