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Muscovite? Missing locality information.

Posted by Anna Merritt  
Anna Merritt September 12, 2017 06:44PM
Hi all, I picked this specimen up from the Denver show (9/2017) because I thought that its triangular crystals were interesting. I am pretty sure that it is muscovite (though the dealer told me quartz); it has the typical "pearly, vitreous luster" of muscovite and it looks like some of the crystals have sheet-like structure. I asked the dealer for locality and he wrote "Mine: Arequipa" , "South of Peru" but I can't really find anything on a single locality with those search terms. I found some other instances of triangular muscovite from NH on mindat (https://www.mindat.org/photo-73662.html, http://www.mindatnh.org/Muscovite%20Gallery.html) but nothing that looks like my specimen. It has some white matrix on the back that I photographed as well. Anybody else have something similar or seen this material before? Thanks in advance for your help.

Ian Nicastro September 12, 2017 08:43PM
Arequipa Department is in southern Peru.


Known for green and pink common opal, Dioptase/Chrysocolla/Copper, and some Rhodochrosite.

What you have there does look like Muscovite to me, specifically from a pegmatite... it's not something I would associate with Peru. I assume it is from Brazil. I swear I can see purplish on a few of the mica faces, suggesting some lepidolite and further suggesting it's from a pegmatite district in Brazil or elsewhere.

Only photos of Muscovite from Peru are this deposit: https://www.mindat.org/gallery.php?loc=219701&pco=1 which does not look anything like your sample. Other mines that have reported muscovite from the dept are porphyry copper, iron and or molybdenum deposits, which shouldn't produce muscovite that looks like this imo.

Edited 1 time(s). Last edit at 09/12/2017 08:46PM by Ian Nicastro.
Anna Merritt September 13, 2017 09:59PM
Thanks Ian for your helpful reply.

Edited 1 time(s). Last edit at 09/13/2017 10:00PM by Anna Merritt.
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