The Naica Mine of the Mexican state of Chihuahua, 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 Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...

mine. Located in Naica in the municipality of Saucillo, the Naica Mine is owned by Industrias Peñoles, the world's largest silver producer.

Caverns A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea ...

discovered during mining operations contain gigantic crystals of (

calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant. One particular hydrate is better known as plaster of Paris ...

di hydrate,

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 drywal ...

, also sometimes called selenite. 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 dep ...

, 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 A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

, 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 Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

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
Naica Mine
at Mindat.org
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