The cave is covered in massive crystals, some reaching as long as 40 feet in length. The cave is extremely hot, with air temperatures reaching up to 58 degrees Celsius with 90-99 percent humidity. The cave is relatively unexplored due to these factors, without proper protection people can only endure 10 minutes of exploration time.
The cave is connected to the Naica Mine near the municipality of Saucillo. The crystals are located nearly a thousand feet below the surface of the mine.
Cave of the Crystals or Giant Crystal Cave (Spanish: Cueva de los Cristales) is a cave connected to the Naica Mine at a depth of 300 metres (980 ft), in Naica, Chihuahua, Mexico.
The main chamber contains giant selenite crystals (gypsum, CaSO4·2 H2O), some of the largest natural crystals ever found. The cave's largest crystal found to date is 12 m (39 ft) in length, 4 m (13 ft) in diameter and 55 tons in weight. When it was accessible, the cave was extremely hot, with air temperatures reaching up to 58 °C (136 °F) with 90 to 99 percent humidity. The cave is relatively unexplored due to these factors. Without proper protection, people could only endure approximately ten minutes of exposure at a time.
The cave was discovered by the brothers Eloy and Javier Delgado. It has since been allowed to re-flood, with the cavern now filled once more with the water rich in minerals required for the crystals to grow.
A group of scientists known as the Naica Project have been heavily involved in researching these caverns.Provided By: https://en.wikipedia.org/wiki/Cave_of_the_Crystals