Post by 1dave on May 7, 2020 0:22:38 GMT -5
earthsky.org/earth/pulpi-geode-formation-process-new-study
The Pulpí geode – discovered in 1999 – is often said to be the biggest geode in the world. Located deep within a mine in Spain – which is open to being viewed by tourists – the geode is a hollow, egg-shaped object, just like those you find in rock shops. But it’s 36 feet (11 meters) long, like a room with crystal-paneled walls. Its individual crystals are up to 6 feet (two meters) in size, and they’re so transparent you can see your hand through them. Scientists are continuing to study the Pulpí geode. A study published October 15, 2019, in the peer-reviewed journal Geology proposed that a slow and steady process involving temperature fluctuations grew the giant gypsum crystals inside it. Juan Manuel García Ruiz is a professor at the Universidad de Granada in Spain and a study coauthor. He said at Phys.org:
Like the giant crystals of Naica in Mexico (see the 2007 Geology article by García-Ruiz and colleagues at … e/35/4/327/129804/), the crystals of Pulpí are gypsum (calcium sulfate with two water molecules). García-Ruiz says, "To reveal their formation has been a very tough task because unlike in the case of Naica, where the hydrothermal system is still active, the large geode of Pulpí is a fossilized environment."
