They're like geodes on steroids. Fisher is the first American to have visited the cavern, which is located near the Penoles-Naica silver, lead and zinc mine south of Chihuahua, and is closed to all but scientific research. Miners had recently uncovered this secondary cavern where these crystals have been found. Still, Fisher and Mexican authorities express concern about possible theft and looting.
Humans can only be in the cavity for a few brief moments before losing consciousness.
Therefore, the depths of the caverns have not even been determined, much less explored. Scientists believe that the selenite crystals emerged in the steam-filled cavern from minerals being deposited by the same hydrothermal fluids that formed the ore deposits. Excess sulfide salts began to develop in the cave from the liquids and hot gases which came up through the Naica fault from the underlying magma or lava bed. Over thousands of years these crystals kept growing larger and larger. Canyon Expert Richard Fisher in his Expedition Shirt .