Naica Mine
[4][5] Caverns discovered during mining operations contain gigantic crystals of CaSO4 · 2 H2O (calcium sulfate dihydrate, gypsum, also sometimes called selenite.
Peñoles announced in October 2015 that it was indefinitely suspending operations due to uncontrollable flooding at the Naica Mine.
[6] The peak underground air temperature was 58°C (136°F) with 100% relative humidity, which rapidly exposed the visitors to hyperthermia hazard and caused breathing difficulties.
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 easier breathing.
[11] If the mining company decides to open another entrance, researchers might again enter to continue their work, according to a February 2019 report.
4 · 2 H
2 O ) in the most spectacular Naica cavern, found during mining. Note the size of the person at the bottom right for the scale.
