[Rockhounds] The world's largest crystal cave

[rik.dillen at skynet.be]

In 1978 I visited an abandoned mine in the Lavrion area (Attika, Greece) together with two local miners who knew the mines like the back of their his hands.
After crawling for a long distance through very narrow pipes and tunnels we reached an extremely big geode, about half the size of the Pulpi geode described below.
Plenty of 5-20 cm aragonite crystals on floor and ceiling... an unbelievable sight!
After our visit one of the two miners requested me not do disclose the exact locality of the geode in the mine, but I must admit that I would never have been capable of describing the 'path' we followed through the labyrinth deep underground.
My back was scratched all over by 'touching' aragonite and other crystals during our crawling trip.
An unbelievable memory for me, but in the meantime access to the mine is no longer possible nor allowed.
A real once-in-a-lifetime experience.
Grts,

Rik Dillen
rik.dillen at skynet.be
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From: Rockhounds <rockhounds-bounces at rockhounds.drizzle.com> On Behalf Of Kreigh Tomaszewski
Sent: Monday, July 25, 2022 14:51
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Subject: [Rockhounds] The world's largest crystal cave

In abandoned silver mine in Pulpí, in Spain's south-eastern Almería Province, lies a treasure that's not made from any precious metal at all.
Instead, what's hidden here is the world's largest geode – a natural crystal phenomenon that has stunned scientists.

As Mila Carretero, geologist and coordinator of the Pulpí Geode, explained, a geode is a cavity inside a rock that is covered with crystals. Sitting against a backdrop of oversized crystal spars, she broke open a tiny rock with tiny gems inside, to show a comparison. "It's the same as the one I have behind me, only this one is a super-sized version," she said with a laugh as she pointed over her shoulder.

The Pulpí Geode is eight metres wide, two metres high and two metres deep.
"When it comes to a geode, by definition, this is the biggest ever discovery," she noted, adding that Pulpí is not to be confused with another crystal marvel, the Naica Mine in Mexico, which has larger spars (15m long compared to Pulpí's two metres), but which is a cave lined with crystals rather than a geode.

The geode here in Spain was originally spotted by miners in the Mina Rica, a silver mine which operated from 1873 to 1969. But it wasn't until years later, in 1999, that geologists found it again and brought it to the world's attention.

"When [the original miners] blasted this rock and found a geode, they probably got upset because they didn't like finding these crystals," said Carretero. "It meant extra work to get rid of them. They weigh a lot and were not profitable."

Though scientists are still researching it, they believe the whole area was once underwater. At a certain point, volcanic activity fractured sedimentary rocks and filled them with hot fluids. When the fluids cooled, the crystals started forming.


https://www.bbc.com/travel/article/20220721-the-worlds-largest-crystal-cave
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