An abandoned mine in Spain conceals a gleaming treasure: the world’s largest geode, a natural crystal phenomenon that has scientists baffled.
In an abandoned silver mine in Pulp, in Spain’s south-eastern Almera Province, there is a treasure made of nothing precious metal at all. Instead, scientists have been astounded by the world’s largest geode, a natural crystal phenomenon.
A geode is a cavity inside a rock that is covered with crystals, according to Mila Carretero, geologist and coordinator of the Pulp Geode. She broke open a tiny rock with tiny gems inside to show a comparison while sitting against a backdrop of oversized crystal spars. “It’s the same as the one behind me, only this one is a super-sized version,” she laughed, pointing over her shoulder.
The Pulp Geode is eight metres across. Two metres high and two metres deep. “By definition, this is the largest geode ever discovered,” she said, adding that Pulp is not to be confused with another crystal marvel, the Naica Mine in Mexico, which has larger spars (15m long compared to Pulp’s two metres), but is a cave lined with crystals rather than a geode.
The geode found in Spain was discovered by miners working in the Mina Rica, a silver mine that operated from 1873 to 1969. But it wasn’t until years later, in 1999, that geologists discovered it again and brought it to the attention of the world.
“They probably got upset when [the original miners] blasted this rock and found a geode because they didn’t like finding these crystals,” Carretero said. “It took more effort to get rid of them. They were heavy and unprofitable.”
Though scientists are still investigating, they believe the entire region was once underwater. Volcanic activity fractured sedimentary rocks and filled them with hot fluids at some point. Crystals began to form as the fluids cooled. Geologists have discovered that the anhydrite (the mineral that formed the rocks) in Pulp dates from around 250 million years ago, but they are unsure about the age of the gypsum crystals themselves because they contain very few impurities that can be dated. They believe the crystals began to form less than 2 million years ago. “The larger the crystal, the slower it grows. And the more perfect the crystal, the more “Carretero stated.
After some rubble was cleared and safety measures, such as a 42m emergency staircase, were installed, the mine was opened to the public in 2019. Workers discovered items left behind by the original miners during the process, such as cigarettes, jackets, rubber sandals, beer bottles, and scratches on the wall tallying their daily quotas.
More than 100,000 people have visited the geode so far, and Carretero’s team is closely monitoring temperature, carbon dioxide, and humidity to ensure the safety of the crystals. “Humidity, rather than carbon dioxide [from human interaction], is what can really harm the crystals,” she explained. “Because if the crystals are coated with a layer of moisture, they lose their transparency.”
However, the crystals of pulp remain remarkably transparent. The natural phenomenon continues to astound visitors and scientists alike. “I couldn’t express how I felt when I saw it,” Carretero said. “It’s indescribable because it makes us realise how insignificant we are. Consider what nature has provided for us.”
A hidden location for the Knights Templar?
Three centuries after it was rediscovered, Royston Cave remains one of Britain’s most mysterious places.
I was looking at a gallery of crudely carved figures, blank-faced and carrying torture instruments, in a hole in the ground beneath the Hertfordshire market town of Royston, dimly illuminated by flickering light. Nicky Paton, the cave manager, pointed them out to me one by one. “Saint Catherine is there, with her breaking wheel. She was only 18 years old when she was martyred “Paton exclaimed cheerfully. “There’s also Saint Lawrence. On a griddle, he was burned to death.”
A large carving of a horse and a fertility symbol known as a sheela na gig, depicting a woman with exaggerated sexual organs, were among the grisly Christian scenes. Another depicted a person holding a candle in their left hand and a skull in their right. The cave is thought to represent an initiation ceremony, providing a tantalising hint as to its possible purpose. The carvings’ rudimentary, almost childlike execution added to their creepiness.
Imagine the surprise of those who, by chance, rediscovered Royston Cave in the summer of 1742. A worker digging foundations for a new bench in the town’s butter market discovered a buried millstone that concealed the entrance to a deep shaft in the earth. In an era before health and safety regulations, a passing small boy was handed a candle and sent down on a rope to investigate, while the people of Royston chattered excitedly above about the possibility of buried treasure.
What was discovered was less profitable but far more mysterious: a broken cup and some jewellery, a human skull and bones, and a human skull and bones. and strange expressionless figures engraved from top to bottom on the walls. Royston Cave remains one of Britain’s most mysterious places three centuries later, with ever more theories about its purpose leading nowhere.
“What draws visitors and historians to the cave is that it remains a mystery as to who built it, when it was built, and why,” Paton explained. “This is primarily due to the lack of documentation regarding its existence prior to its accidental discovery. There were no books, drawings, or diaries to suggest it was even present.”
What makes the cave so intriguing to visitors and historians is that it’s still an enigma; still a mystery as to who made it, or when or why
There are, however, numerous theories. Those of an esoteric bent claim that the cave is located at the crossroads of two ley lines – ancient pathways thought to connect places of spiritual power – one of which, the so-called Michael Line, also runs through Stonehenge and Avebury.
The cave lies directly beneath the intersection of two historically significant ancient roads: the Icknield Way, a historical trackway that runs from Norfolk to Wiltshire along southern England’s chalk escarpment, and Ermine Street, a Roman road that originally ran from London to York. A large footstone now stands in place of a cross that once stood at the intersection of these two roads, named after Lady Roisia. Royston is thought to have been named after a local noblewoman.