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Mathias
Joined: 01 Apr 2018
Posts: 146
Location: Vlodrop
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Posted: Dec 01, 2019 07:56 Post subject: Uknown mineral specimen |
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Dear FMF friends,
Today I purchased a specimen that came with the following label: "Psilomelane, Brazil".
The vendor said that he actually doesn't know what it is, he got the specimen as one of a large, mainly undocumented, collection. I believe that it isn't psilomelane.
The specimen is approximately 10 cm, I thought it might be Quartz after Aragonite. But looking on internet, I can't find any similar specimen.
Is there anybody who recognizes this mineral?
Thanks,
Mathias
Dimensions: | 10 cm * 8 cm * 5 cm |
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Mathias
Joined: 01 Apr 2018
Posts: 146
Location: Vlodrop
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Posted: Dec 01, 2019 09:23 Post subject: Re: Uknown mineral specimen |
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There's some additional information:
When I point a laserlight on the reddish portions of the specimen, the area lightens up by dispersion of the laser beam. So these portions are opaque.
You wouldn't expect such properties in case of psilomelane or otherwise iron oxides.
Best regards,
Mathias.
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Kevin Conroy
Joined: 03 Dec 2018
Posts: 78
Location: Saint Louis, Missouri
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Posted: Dec 01, 2019 09:35 Post subject: Re: Uknown mineral specimen |
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Hi, I think that this is probably chalcedony after aragonite from Valle de las Plumas, Argentina.
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alfredo
Site Admin
Joined: 30 Jan 2008
Posts: 979
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Posted: Dec 01, 2019 10:29 Post subject: Re: Uknown mineral specimen |
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I agree with Kevin about the ID and the locality.
Nice pseudomorph!
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Roger Warin
Joined: 23 Jan 2013
Posts: 1176
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Posted: Dec 01, 2019 15:10 Post subject: Re: Uknown mineral specimen |
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Yes, I think so.
Here is a chacedony covered with limonite psm after barite.
Mineral: | limonite after Baryte |
Locality: | Kipushi, Katanga Copper Crescent, Katanga (Shaba), Democratic Republic of the Congo (Zaire) | |
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