Acanthite : Ag2S, Calcite : CaCO3, Pyrite : FeS2

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Copyright © Helen Tyson
minID: LEK-7CM

Acanthite : Ag2S, Calcite : CaCO3, Pyrite : FeS2

Copyright © Helen Tyson  - This image is copyrighted. Unauthorized reproduction prohibited.
Dimensions: 5 cm x 3 cm

This acanthite with monoclinic xls crystallised below the transition temperature to cubic argentite. This is from the type locality for Acanthite.

Herb Obodda got this piece from the natural history museum in Paris, but Schubnel didn't give him the red label from when it belonged to the Austrian Emperor. That red label was probably worth more than the specimen.

I no longer have the specimen and Herb misidentified the paper spar calcite as barite and Schubnel is wrong about proustite. Please see: http://www.mindat.org/mesg-106-323362.html

ROM collection, ex RWMW collection, Helen Tyson photo

This photo has been shown 505 times
Photo added:2nd May 2014
Dimensions:2048x1536px (3.15 megapixels)

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Discuss this Photo

PhotosAcanthite - Jáchymov, Jáchymov District, Krušné Hory Mtns, Karlovy Vary Region, Bohemia, Czech Republic

2nd May 2014 21:24 BSTRichard Gunter Expert

I think you might check the identity on this one. Ondrus (2003) makes a clear distinction between the rhombohedral, white Calcite that occurs with ore minerals (see my Acanthite) and the "paperspar" (he uses the German equivalent name) that is a late phase associated with: Smythite, Sternbergite, Cinnabar, Imiterite and Pyrrhotite. Is it possible the "Proustite" may be Imiterite long before it was characterized?

2nd May 2014 21:49 BSTRob Woodside Manager

Thanks Richard. Sadly I no longer have the specimen, but I'm sure the ROM would sacrifice a grain for EDS. I just have to get to Toronto. When Rod cleaned it it came up like you see now. Previously it was dull and black. I think Herb's Barite might be paper spar rather than Barite. Most paper spar seems not stacked like these. Perhaps other more familiar with this material might comment. A low temperature Late Stage makes sense for acanthite.

2nd May 2014 21:58 BSTRichard Gunter Expert

Hi Rob:

Ondrus says that Baryte is very rare at Jachymov and does not occur with Acanthite.

2nd May 2014 22:34 BSTRob Woodside Manager

Thanks Richard . I'll fix it

2nd May 2014 23:02 BSTRichard Gunter Expert

Hi Rob:

It will be interesting to see what the EDS turns up.
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