ENVIRONMENT
Crystal giants Deep under a Mexican desert lies a mysterious cave that’s beautiful but deadly
T
wo brothers were drilling in the Naica mine in Mexico when they uncovered a geological wonder of the world, hundreds of thousands of years in the making. The Cueva de los Cristales, or Cave of Crystals, is a glittering palace covered in some of the largest crystals anyone has ever seen. Measuring over 11 metres – roughly the length of a bus – they have thrived in the extreme conditions of the cave. Temperature is a sweltering 44 degrees Celsius and up to 100 per cent humidity means the air you breathe quickly condenses inside your lungs. Geologists hell bent on exploring the cave and living to tell the tale had to don specially designed suits, strewn with ice packs. If they had taken their respirator mask off for more than ten minutes, they would have fallen unconscious. However, what proves deadly for humans are the perfect conditions for growing crystals. These monstrous structures are made of a soft mineral called selenite, and formed from groundwater saturated with calcium sulphate, which was heated by a magma chamber below. As the magma cooled, the minerals in the water started to transform into selenite and steadily built up. The cave’s oldest resident is 600,000 years old – forming at the time when the ancestors of modern humans first appeared! The crystals only stopped growing when miners unintentionally drained the cave in 1985 while they lowered the water table. But when the mine stops being profitable, the owners of the Naica mine will remove the pumps and the cave will flood once more. The crystals will be lost, but we can take comfort in knowing there must be more hidden marvels like this. “We know more about the outer edges of the Solar System than we do about the first kilometre of the Earth’s crust,” Professor Iain Stewart told the BBC after exploring the caves. “We can be sure there will be discoveries even more spectacular than Naica.”
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