Giant Crystal Cave’s Mystery Solved

It’s “the Sistine Chapel of crystals,” says Juan Manuel García- Ruiz.

Mexico’s Cave of Crystals contains some of the world’s largest known natural crystals—translucent beams of gypsum as long as 36 feet (11 meters). A new study says the gems reached their vast sizes thanks to a peculiar combination of consistent volcanic heat and a rich watery mixture.

The geologist announced this week that he and a team of researchers have unlocked the mystery of just how the minerals in Mexico’s Cueva de los Cristales (Cave of Crystals) achieved their monumental forms.

Buried a thousand feet (300 meters) below Naica mountain in the Chihuahuan Desert, the cave was discovered by two miners excavating a new tunnel for the Industrias Peñoles company in 2000.

The cave contains some of the largest natural crystals ever found: translucent gypsum beams measuring up to 36 feet (11 meters) long and weighing up to 55 tons.

“It’s a natural marvel,” said García-Ruiz, of the University of Granada in Spain.

To learn how the crystals grew to such gigantic sizes, García-Ruiz studied tiny pockets of fluid trapped inside.

The crystals, he said, thrived because they were submerged in mineral-rich water with a very narrow, stable temperature range—around 136 degrees Fahrenheit (58 degrees Celsius).

At this temperature the mineral anhydrite, which was abundant in the water, dissolved into gypsum, a soft mineral that can take the form of the crystals in the Naica cave.

The new findings appeared in the April issue of the journal Geology.