An international study led by the Higher Council for Scientific Research, CSIC , concludes that the crystalline gypsum formations of the Mexican Naica mine grow at a rate equivalent to the thickness of a hair every 100 years . This is the slowest growth rate ever recorded, so much so that a special microscope has been required to measure it.
The Cueva de los Cristales de Naica is located 300 meters underground in the Mexican desert of Chihuahua . Discovered in 2000 in the vicinity of a lead mine, it astonished the world by the enormous dimensions of the selenite crystals found there, the largest in the world. Since then, scientists have tried to analyze the peculiarities of this surprising cave and answer some questions: how is it possible that such pure and transparent crystals grew so much? How long did it take to do it? Now, and with the help of new technologies, some unknowns seem to begin to be cleared up.
According to Juan Manuel García Ruiz, researcher at the CSIC, “The growth of these formations is so slow that until now it was almost impossible to measure. In this study we have achieved it thanks to a special microscope that we have designed in collaboration with a research group from Senda University, Japan. This instrument has allowed us to estimate that some of the crystals in the cave have been growing for about a million years . “
The research also aimed to analyze the reactivity of the gypsum to the groundwater of the Naica mines, which flooded the Cave of the Crystals during the entire growth process and allowed the formation of these enormous selenites. Today, crystal growth remains stagnant because work in the mines to extract silver, lead and zinc has not stopped and the cave lacks water.
Precisely, the stability of humidity and temperature are the most relevant variables for the formation of these crystals in the eyes of scientists. As García Ruiz himself sums up, “the air temperature in the cave is around 50 degrees Celsius and has a humidity above 90 percent. The selenites began to grow when the temperature dropped below 58 degrees and since then it has cooled down to the current temperature, but it does so very slowly thanks to a hot spot located about four kilometers deep. “
