[Rockhounds] The world's largest crystal cave

[rik.dillen at skynet.be]

Hi Alan,

As English is not my mother tongue, obviously I do not know much about the
correct terms when it comes to subtle or even less subtle differences.
I suppose you're right, and in that case what I have seen in Greece was also
a vug, not a geode.

In Dutch I found the following on Wikipedia-NL
(https://nl.wikipedia.org/wiki/Geode):
>>>>> Een geode of druse is een holle of gedeeltelijk holle, min of meer
bolvormige knol die aan de binnenkant begroeid is met kristallen. Meestal
zijn geoden tussen de 2,5 en 30 centimeter groot, maar dit kan sterk
variëren.... (snip)... Een geode bestaat uit een dunne maar hechte
buitenlaag van silicaten, meestal gevuld met een laag kwartskristallen zoals
amethist of rookkwarts, maar er kan zich ook calciet in bevinden.
>>>>> [A geode or 'druse' is a hollow or partly hollow, more or less
spherical nodule with an inner surface lined with crystals. Mostly geodes
are 2.5 to 30 cm, but that can vary... (snip)... A geode consists of a thin
but tight outer layer of silicates, mostly filled with a layer of quartz
crystals such as amethyst or smoky quartz, but it can also be calcite.] 

Anyway it was a splendid view in the light of our lamps, and an
unforgettable experience.

Grts,

Rik Dillen
rik.dillen at skynet.be
Mineralogische Kring Antwerpen - www.minerant.org
Lid worden van de MKA ?  www.minerant.org/MKA/lidworden.html

MINERANT 2023 - 6 en 7 mei 2023
Antwerp Expo

-----Original Message-----
From: Rockhounds <rockhounds-bounces at rockhounds.drizzle.com> On Behalf Of
Alan Goldstein
Sent: Wednesday, July 27, 2022 1:59
To: Rockhounds at drizzle.com: A mailing list for rock and gem collectors
<rockhounds at rockhounds.drizzle.com>
Subject: Re: [Rockhounds] The world's largest crystal cave

I realize that like the word "theory," geode has multiple definitions. I've
read that - in geological terms - a geode is quartz-lined somewhat spherical
rock within sedimentary or igneous rocks and a "vug" is a hollow pocket
lines with crystals (no quartz rind). With that in mind, the beautiful
calcite-lined cavity in Spain is a vug. What have you read about the
difference between a geode and vug?

Alan G.
________________________________
From: Rockhounds <rockhounds-bounces at rockhounds.drizzle.com> on behalf of
Kreigh Tomaszewski <kreigh at gmail.com>
Sent: Monday, July 25, 2022 8:51 AM
To: Rockhounds at drizzle.com: A mailing list for rock and gem collectors
<rockhounds at rockhounds.drizzle.com>
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.


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