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Jordi Fabre
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Posted: Apr 22, 2009 15:52 Post subject: Re: Practical Mineralogy #1: Pyrite pseudomorph after Pyrrhotite - (2) |
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Peter,
Please add to the list the locality of El Hamman, Meknes, Morocco. As soon as I can I will publish a photo of a very nice example from there.
Jordi
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Jesse Fisher
Joined: 18 Mar 2009
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Location: San Francisco
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Posted: Apr 22, 2009 17:18 Post subject: Re: Practical Mineralogy #1: Pyrite pseudomorph after Pyrrhotite - (2) |
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Peter,
Here is a photo of pyrrhotite from the Cambokeels Mine in Weardale. The field of view is about 2.5 cm across. I'm pretty sure it at least pyrrhotite to begin with as a number of sections on the surface appear to be "tiled" with small hexagonal plates. As mentioned, no hint of magnetism.
Jesse
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Pyrrhotite (possibly pseudomorphed by pyrite) from the Cambokeels Mine, Weardale, England. 2.5 cm across. |
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alfredo
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Joined: 30 Jan 2008
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Posted: Apr 22, 2009 21:51 Post subject: Re: Practical Mineralogy #1: Pyrite pseudomorph after Pyrrhotite - (2) |
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You're probably right about the pyrrhotite, Jesse, but just in case, check the streak. There are some weird metallic-tarnished wurtzites in Bolivia that have that same stacked-hexagonal-tiles appearance, and a nice black streak would ensure that that tiny bit of doubt could be eliminated.
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Jesse Fisher
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Posted: Apr 22, 2009 23:08 Post subject: Re: Practical Mineralogy #1: Pyrite pseudomorph after Pyrrhotite - (2) |
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Dark gray/black it is.
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Jordi Fabre
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Posted: Apr 23, 2009 06:12 Post subject: Re: Practical Mineralogy #1: Pyrite pseudomorph after Pyrrhotite - (2) |
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Here you have the promised image of a Pyrite after Pyrrhotite (and Pyrite coating) from the Fluorite mine of El Hamman, Meknes, Morocco.
Jordi
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Pyrite after Pyrrhotite coated with a second generation of Pyrite and placed in a Quartz matrix. El Hamman, Meknes, Morocco Specimen size: 9 x 4.5 cm. Crystals size: 2.2 x 2.2 cm. Mined in 2008 Collection: Jordi Fabre |
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Peter Megaw
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Location: Tucson, Arizona
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Posted: Apr 23, 2009 10:10 Post subject: Re: Practical Mineralogy #1: Pyrite pseudomorph after Pyrrhotite - (2) |
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Cool pictures guys, great discussion...keep it up PLEASE
_________________ Siempre Adelante! |
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alfredo
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Posted: Apr 23, 2009 15:39 Post subject: Re: Practical Mineralogy #1: Pyrite pseudomorph after Pyrrhotite - (2) |
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Peter, If you were a subscriber to Rocks & Minerals back in 1998, there was an article on a variety of pseudomorphs from Bolivia in vol. 73, # 6, pp 410-414.
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alfredo
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Posted: Apr 24, 2009 14:58 Post subject: Re: Practical Mineralogy #1: Pyrite pseudomorph after Pyrrhotite - (2) |
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Am currently enjoying the Rochester Symposium in western New York state. A few other FMF friends are here, including John White, and Gail. In the display cases there are a number of fine pseudomorph specimens that might be relevant to Pete's study:
Siderite @ pyrrhotite - Turt, Rumania
Siderite @ calcite - Turt, Rumania
Galena @ pyrrhotite - Herja, Rumania
Siderite @ calcite - Gheturi mine, Rumania (Not in Mindat; do you know it, Jordi?)
Siderite @ calcite - Boldut, Rumania
Siderite @ calcite - Broken Hill mine, Aggeneys, South Africa
Tennantite @ chalcocite - Tsumeb
Tennantite @ enargite - Anselmo mine, Butte
Stolzite @ scheelite - Thompson mine, Darwin, CA
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Jordi Fabre
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Posted: May 09, 2009 07:27 Post subject: Re: Practical Mineralogy #1: Pyrite pseudomorph after Pyrrhotite - (2) |
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Another image of a Pyrite after Pyrrhotite from Sultana Quarry, Cartagena, Murcia, Spain. On this case covered by Sphalerite.
Description: |
Pyrite after Pyrrhotite and Sphalerite Sultana Quarry, Cartagena, Murcia, Spain 12 X 10 cms. Photo and specimen: Felipefosil ( http://www.foro-minerales.com/forum/viewtopic.php?p=20265#20265 ) |
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Azogue
Joined: 04 Sep 2009
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Posted: Sep 04, 2009 09:06 Post subject: Re: Practical Mineralogy #1: Pyrite pseudomorph after Pyrrhotite - (2) |
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I am rather late to enter the discussion!
Anyway, I just fell on your question: "does anyone know of a Sn component in (a few world ore deposits) and Trepca.
The answer for Trepca is YES. Stannite (but just a little!). The run of mine ore contains around 36 ppm Sn.
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mmauthner
Joined: 30 May 2007
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Location: Graz
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Posted: Sep 04, 2009 10:11 Post subject: Re: Practical Mineralogy #1: Pyrite pseudomorph after Pyrrhotite - (2) |
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OK, many months down the line, but I finally located an old image of a pyrite pseudomorph after pyrrhotite from the Nanisivik mine. Unfortunately, I took this with a Nikon 990 over ten years ago, of course in jpg format, which has had years of compression artifacts added. Second, the specimen has since gone to its next mineralogical life as a pile of rubble and sulphuric acid.
Note that this is unequivocally a "pyrrhotite" habit and could not be mistaken for a twinned marcasite. The pyrite after marcasite pseudomorphs I find hard to imagine as being confused with pyrite after pyrrhotite as the angles are quite a bit different. Pyrrhotite rosettes are hexagonal with axis angles at 60 degrees from one another; twinned marcasite looks more like "fivelings" (never complete; usually only up to three axes showing) with axes at 75 degrees to one another.
Cheers,
Mark
Description: |
Pyrite pseudomorph after pyrrhotite. Nanisivik min, Baffin Island, Nunavut, Canada. About 3.5 cm across. |
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Jordi Fabre
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Posted: Sep 29, 2009 03:08 Post subject: Re: Practical Mineralogy #1: Pyrite pseudomorph after Pyrrhotite - (2) |
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Not exactly Pyrite after Pyrrhotite but quite interesting, I believe. It is from Turt, Satu Mare, Rumania where other Pyrites after Pyrrhotite appeared in the past.
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Chalcopyrite after Pyrrhotite rosettes with Galena and minor Sphalerite. Turt, Satu Mare, Rumania Mined in 2000 Specimen size: 10.5 × 8.5 cm = 4.1” × 3.3” Photo: Reference Specimens -> http://www.fabreminerals.com/specimens/RSRO-rumania-notable-specimens.php#T62Q |
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Peter Megaw
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Posted: Sep 29, 2009 07:19 Post subject: Re: Practical Mineralogy #1: Pyrite pseudomorph after Pyrrhotite - (2) |
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Mark and Jordi...glad to see the thread is alive...thanks for both pictures.
Mark, I agree these are clearly ex-pyrrhotite...and on peripheral note I am not surprised they have disintegrated, from what I've seen, the thin platy habit of both pyrrhotite and py ps po seem quite a bit more prone to alter than more elongate crystals.
Jordi, are there any places you can see how far the chalcopyrite has "eaten" into the pyrrhotite and/or is there any residual pyrrhotite left? a magnet can tell.
Satu Mare seems to be fit very nicely with the long-lived, multi-stage genesis hypothesis, which is also exemplified by multple pseudomorphing relationships. Northstar Minerals website is worth a look on this...multiple photographs of elegant pseudomorphs (This is not intended as a plug for Ross...although he deserves it...just a recommendation to check out his pictures)
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Jordi Fabre
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Posted: Sep 29, 2009 10:42 Post subject: Practical Mineralogy #1: Pyrite pseudomorph after Pyrrhotite - (2) |
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Peter Megaw wrote: | Jordi, are there any places you can see how far the chalcopyrite has "eaten" into the pyrrhotite and/or is there any residual pyrrhotite left? a magnet can tell. |
Yes Peter, some former Pyrrhotite remained there. I haven't the specimen but I remeber so well the residual Pyrrhotite.
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