The Mystery of the Giant Crystals: How the 36-foot Geode of Pulpí Formed
There is a room of pure crystal in an abandoned mine in Southern Spain.
You have to go down to the deep tunnel, climb a rock ladder and squeeze across a twisted, barely wide gypsy crystal tube. When you get that point, you’ll be in the largest geode of the world: the Pulpí Geode, a cavern of 390 cubic feet about the size of a mixer drum, filled with crystals as smooth as ice and sharp as spears on all surfaces.
Though you might never have stood in a geode, you probably held one before or at least saw it.
Juan Manuel García-Ruiz, a geologist at the National Research Council of Spain and co-author of the new paper on the history of the Pulpí Geode, told BBC “Some people have little geodes in their homes,” he added.
Those crystals can form after water flows into the hollow inside through small pores on a rocky surface. The caches of amethyst, quartz, and many other light minerals may continue to grow for thousands of or millions of years, depending on their size.
Gypsum is the result of salt, calcium sulfate and a lot of time in the crystal columns of Pulpí, but nothing more has been discovered since the sudden geode discovery of 2000.
García-Ruiz and his colleagues tried to give a new light to the enigmatic cave by minimizing the geode’s shape in a study published in the journal Geology.
It’s not an outsider to giant crystals García-Ruiz. In 2007, the author published a study of the fantastical Mexican Cave of Kristals, a gypsum beam cavern of a basketball courtyard as wide as a telephone pole, that had been buried at 300 meters below Naica’s city. The fact that the crystals still formed in the damp bowels of the mine made it easier to explore the past of the “Sistine Capila,” as García-Ruiz called it.
In Pulpí, however, the mine was completely dry and in tens of thousands of years, geodesic crystals did not grow. On top of that, Garcia-Ruiz said: “You can see your hand through them, but the spikes of the geode are amazingly white.
It means that there is no uranium isotope in sufficient quantities for radiometric dating, a common technique for evaluating the depletion of very old rocks of different versions of the elements ..
Garcia-Ruiz said, “We didn’t know what happened.” And, to understand its very complex geology, we had to cartograph the whole mine.
For seven years, the scientists studied and radiometrically dated rock samples around the mine to determine how it had evolved since its formation centuries ago. The guiding question of the project is where the Pulpí Geode calcium sulfate came from?
The researchers eventually shortened the formation of the geode to around 2 million years (not bad for the 4.5-billion-year geological calendar). The crystals must be 60,000 years or so, the team has found that this is the youngest age of some carbonate crust in the geodes. García-Ruiz clarified that because the crust is at the end of a crystal the crystal below must be older.
In the meantime, the composition of the other minerals in the mine indicates that only after an event known as the Messinian salinity crisis, calcium sulfate was added into this region – the almost complete Mediterranean Sea extinction which has been recorded to be about 5.5 million years ago.
Based on the size of the gypsum crystals, it is possible that they began to form less than 2 million years ago, through a very slow-growing process called Ostwald maturation, in which massive crystals develop through the dissolution of smaller ones, García-Ruiz said. Pay attention to your freezer for a regular example of this.
As ice cream grows old, small ice crystals start breaking off the remainder of the product. When time passes, these small crystals are lost and recombined into larger crystals, giving that extremely trash appearance of the old ice cream.
The Pulpí Geode is definitely not so good as the ice cream, but it just has its sweet pleasure to learn that beautiful places like that exist.
Due partially to planning activities by the research team, visitors can now explore the Pulpí Geode, which would definitely not be the responsibility of García-Ruiz. For the first for years, García-Ruiz was slipping past the jagged gypsum portal and in the Geode cavity.