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Posted by Rock Currier  
Daniel J. Evanich January 13, 2012 05:46PM
Here is an interesting old collection Butte, Montana, specimen of acanthite after polybasite (with malachite coating) that was analyzed in 2011 by John Attard and confirmed as such.

About three years prior, I purchased a box of five or six "ore" specimens from Butte, and noticed a few that were off-color from the usual black and brass sulphides seen from this classic American locality. One had a green coating along with a handwritten label calling out polybasite and its formula. I've read about similar examples from The Anselmo Mine and Star West Mine in Butte, but not actually seen one. The specimen is about 5cm in width with individual crystals in the 1.0-1.5cm size coated with green malachite (analyzed).

Does anyone have any comment on the specific mine occurences of acanthite/polybasite from Butte, Montana?

Edited 1 time(s). Last edit at 01/13/2012 09:12PM by Rock Currier.
open | download - Acanthite after Polybasite with Malachite--Butte Montana004_edited.JPG (273.2 KB)
open | download - Acanthite after Polybasite with Malachite--Butte Montana001_edited.JPG (281.4 KB)
open | download - Acanthite, USA, Butte @ polybasite1 copy.jpg (145.7 KB)
Rock Currier January 13, 2012 09:01PM
Thanks for your picture of the acanthite after polybasite. I think a more appropriate place to post it would be in one of the other forums of the message board rather than best minerals. At any rate before we could consider using it in best minerals the images would have to be uploaded to the Mindat database rather than just an attachment to a message board post. If you would like to do this I can help you there. You might also wish to consider running it through Photoshop or a similar program to improve the quality of the image. See the example in your post that I took the liberty of editing a little and including in the body of your post. I think that the specimen might be better placed in the Best Minerals pseudomorph A to C article.

Rock Currier
Crystals not pistols.

Edited 1 time(s). Last edit at 01/13/2012 09:13PM by Rock Currier.
Daniel J. Evanich January 14, 2012 03:33AM
Thanks, Rock. Appreciate the advise. I did post higher res images to the regular Mindat site under acanthite just after this post. See you in Tucson for the BAM dinner on either Thursday, the 9th, or Friday the 10th, yet to be determined. Once again, NO LOUD MARIACHIS allowed.........
Anthony Scoffler August 31, 2017 05:36AM
For the Mexico, Guanajuato, Rayes Mine locality, the first picture shows acanthite with "chalcoprite", which should be typed chalcopyrite. Just pointing out this tip in the hopes it'll be useful.
Paul De Bondt August 31, 2017 11:51AM
Thanks Anthony, done.
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