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GeneralHelp with modified fluorite from Spain

21st Sep 2014 04:57 UTCJuan Fernandez Buelga

05906180016061406586503.jpg
Hi everyone,


I'm not sure if this is the correct section for this topic.


I would like to know if anyone has seen this type of dodecahedral modification before. Looks like a normal fluorite cube very slightly modified by the dodecahedron, but on one of its corners it presents a very well developed "dodecahedral modification" plus many fine lines on each side. I've never seen something similar before. The rarely modified crystal is around 1cm and the specimen is around 3cm.From La Viesca Mine, Asturias, Spain.


I would love to see similar modified fluorites.


Thanks in advance for you help!


Juan Fernandez Buelga


00010870016010399241193.jpg

00548210016010399253503.jpg

21st Sep 2014 09:09 UTCErik Vercammen Expert

These lines are formed by the contact with another mineral that was growing at the same time, maybe calcite. You can see on the pictures that this corner is not as large as the other ones, just because of the growth inhibition. Nice specimen.

21st Sep 2014 19:37 UTCNik Nikiforou

I agree with Eric. These are not modifications, rather they are the imprint of adjacent crystals which are no longer present.

29th Sep 2014 07:47 UTCJuan Fernandez Buelga

Sorry Nik, but the crystal is clearly modified. I know what you mean, but this is not that case. I will try to upload a photo of the case you are speaking about.


Thanks Erik for your interesting input.

30th Sep 2014 05:11 UTCBob Jackson 🌟 Expert

Sorry, Juan, but I agree with Nik and Eric. I've found very similar lines on Berbes fluorites where two adjacent cubes separated during growth. I'd call it a former contact.


Identical patterns are very common on Navajun and Spruce pyrite cubes, and I suspect many other isometric minerals.


Bob

5th Oct 2014 03:42 UTCJuan Fernandez Buelga

08480480016061406581882.jpg
Hi all,


I have just photographed a fluorite specimen from Berbes which shows the lines you are talking about (it is very common to see them in broken specimens). It is not the best example to show these lines, but I will try to post better examples when I can.


Bob: As you say they are similar, but it is not the same case. Crystals don't need to separate during growth to form these lines, you can just grab an specimen with several fluorite crystals, break apart the specimen where two crystals join and you will find them quite easily. Those lines are created during crystal growth.


As you can see they are not like the ones you can see in the first photo I posted. Moreover you can not find the dodecahedral faces anywhere.


04568980016010399254477.jpg

5th Oct 2014 13:04 UTCOwen Melfyn Lewis

05820780016031651284726.jpg
Juan,

You have a modifed fluorite.


Here's mine, albeit very small, as an inclusion in a cabbed topaz.


 
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