Meet the Cave of the Crystals – Giant Selenite Crystal Cave in Mexico

The Cave of the Crystal or the Giant Crystal Cave is a fascinating selenite cave in Naica, Chihuahua, Mexico. The cave was discovered in 2000 by miners who were excavating a new tunnel in the Naica Mine at a depth of approximately 300 meters (980 feet) below the land surface. Earlier, in 1910, a smaller room named the Cave of Swords was discovered at a depth of 120 meters (390 feet), above the Cave of the Crystals. The Cave of Swords contains amazing one-meter long selenite crystals covering the walls.

How the Giant Crystal Cave was Discovered

Brothers Juan and Pedro Sanchez, miners drilling in the Naica Mine to excavate a new tunnel for the Industrias Peñoles mining company, discovered the Giant Crystal Cave in April 2000. They were drilling through the Naica fault at the time. The Naica Mine is well-known for rich deposits of silver, zinc, and lead.

Inside the Cave of the Crystals with Massive Selenite Gypsum

The giant cave is located in limestone rock and is shaped like a horseshoe. The floor of the cave is covered in selenite gypsum blocks. The large blades rise from the blocks and the cave floor at varying angles throughout the cave. The Cave of the Crystals has spectacular, giant selenite gypsum crystals that are over 12 meters (39 feet) in length and 4 meters (13 feet) in width and weigh over 55 tons! These gypsum crystals are among the largest in the world.

The cave itself is very difficult to explore. The natural air temperatures inside the cave reach 136F with 90 to 99 percent humidity making it impossible to visit until you have protective clothing and equipment. Studying the cave has been a difficult challenge for scientists given the high temperature and humidity. Researchers must wear special protective suits that keep the body cool and provide fresh air. Even with the cooling suits, scientists were only able to spend between 30 and 45 minutes in the cave during each visit.

Selenite Mineral Properties

Selenite is a form of the mineral gypsum, also called Satin Spar. Satin spar is a fibrous variety of the mineral which forms in long strands, which grouped, form “sticks.” The following are the properties of the selenite mineral.

  • Chemical Formula:  CaSO4 . 2H2O
  • Color:  Colorless or White
  • Crystal Shape:  Tabular. Also may form twins or rosettes.
  • Cleavage:  Perfect
  • Fracture:  Conchoidal to splintery
  • Hardness:  2 on Mohs Hardness Scale
  • Streak:  White
  • Luster:  Pearly to Glassy
  • Density: 2.308 g/cm3
  • Uses:  Paints, Tile, Drywall, Blackboard Chalk, Fertilizer, Plaster of Paris

How the Selenite Crystals Formed Inside the Giant Crystal Cave

Scientists believe that the selenite crystals in the Giant Crystal Cave took approximately 500,000 years to grow to their current size. The heat in the cave results from a pool of liquid magma located approximately two to three miles below the main room of the cave. The cave periodically floods with water rich in gypsum minerals. The heat from the magma allows the selenite crystals to form from the mineral-rich water. The crystals form very slowly over a long time, which is why the selenite sticks are so huge.

Add Selenite to Your Collection

Mini Me Geology carries beautiful samples of selenite sticks, natural gypsum, and gypsum roses. These are fantastic minerals to add to your collections and they make a great gift for rockhounds as well! If you have any questions about any of our gypsum samples, please let us know.

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