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Cueva de los Cristales

‘Cueva de los Cristales’, or, ‘Cave of Crystals’, is a giant underground cave containing some of the largest, naturally growing crystals ever found on earth. It is situated 300 metres below the surface in Naica, Chihuahua, Mexico. The crystals here are formed of selenite or gypsum and are a brilliant, clear, luminous white. The largest crystal here measures 12 metres in length, 4 metres in diameter and weighs an estimated 55 tons!

Conditions in the cave

Despite being discovered in 2000, much of the cave still remains relatively unexplored. This is largely due to the harsh conditions found at these depths, where humans can only tolerate approximately ten minutes at a time without protection. The air temperature reaches a stifling 58°C and the humidity hovers at around 90% to 100%.

Crystal formation

Naica lies on an ancient fault above an underground magma chamber. The hollow space of the cave became filled with a mineral rich ground water heated by the magma below. The water temperature stabilised at over 50°C and remained so for around 500,000 years. This allowed crystals to form and to grow to the immense sizes that we see today.


It is a 20 minute van drive through the Naica Mine to reach the cave. Explorers would look more at home on the moon than in a mine once they are kitted up and ready to enter. The average tour lasts only 20 minutes, even strapped with ice packs and breathing super cooled air. But the trip is worth the effort. Spanish crystallographer, Juan Manuel García-Ruiz, one of the first to study the cave, called it the Sistine Chapel of crystals. Others liken it to an extraterrestrial experience or to being inside a tomb. But my favourite quote comes from a local. “It is like a child’s dream”.

If you have any gemmological curiosities that you would like to have valued then please contact Simon Rufus, gemmologist at Grand Auctions, Folkestone, Kent.