The spectacular Giant Crystal Cave is connected to the Naica Mine, located in Chihuahua, Mexico.It goes around 300 meters below the surface. The main chamber contains the largest selenite crystals ever found, some of them reaching 11 meters in length, 4 meters in diameter and about 55 tons in weight.
The conditions here are extreme, with a constant temperature of 58 °C and high humidity, proving to be a dangerous environment for those who are exposed more than 10 minutes without proper equipment. The crystals are said to be 500,000 years old and were formed from the underground magma (situated below the cave) which maintained the water at a stable temperature of 50°C, saturating it with minerals, including gypsum.
This process allowed the selenite crystals to grow to the unbelievable sizes that we see today.
The Cave of the Crystals in Mexico can only be visited under direct professional supervision. You can read more fascinating details about the crystal cave on BBC or on the official website of the Naica scientific project.
An extended and well-written journal about the adventure you see in these stunning photos can be read on National Geographic.