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David K. Joyce
Joined: 15 Dec 2018
Posts: 20
Location: Canada
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 Posted: Oct 29, 2020 17:01 Post subject: Re: Unusual bar pyrite from Nanisivik |
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| I'd look forward to seeing them! Thanks, DKJ |
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Bob Morgan
Joined: 18 Jan 2018
Posts: 251
Location: Savannah, Georgia
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| Posted: Oct 29, 2020 17:52 Post subject: Re: Unusual bar pyrite from Nanisivik |
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Your sample is definitely not pyrite over marcasite. I have several elongated specimens from there, one a bunch of simi aligned bars that compose a tube, another that is a pseudomorph of elongated marcasite blades, and the striations do not run the same way as in your sample.
Pete Richards et all wrote an article on such epitaxy and illustrates the differing pattern of crystal alignment and striations. See Pyrite and Marcasite Intergrowths from Northern Illinois, Mineralogical Record, 26, March-April 1995.
The only slight possibility of epitaxy might be suggested by photo 95G-8NW in Mindat, but even that doesn't resemble your sample.
Another photo does: R24-FUP. That one raises the mystery even higher. Surely there is some structural explanation for the consistent elongations. Perhaps overgrowths of pyrite whiskers? |
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RussEpp
Joined: 27 Oct 2020
Posts: 14
Location: Manitoba
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| Posted: Oct 29, 2020 18:33 Post subject: Re: Unusual bar pyrite from Nanisivik |
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| Bob Morgan wrote: | Your sample is definitely not pyrite over marcasite. I have several elongated specimens from there, one a bunch of simi aligned bars that compose a tube, another that is a pseudomorph of elongated marcasite blades, and the striations do not run the same way as in your sample.
Pete Richards et all wrote an article on such epitaxy and illustrates the differing pattern of crystal alignment and striations. See Pyrite and Marcasite Intergrowths from Northern Illinois, Mineralogical Record, 26, March-April 1995.
The only slight possibility of epitaxy might be suggested by photo 95G-8NW in Mindat, but even that doesn't resemble your sample.
Another photo does: R24-FUP. That one raises the mystery even higher. Surely there is some structural explanation for the consistent elongations. Perhaps overgrowths of pyrite whiskers? |
Actually R24-FUP is the same specimen as the one in discussion. |
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RussEpp
Joined: 27 Oct 2020
Posts: 14
Location: Manitoba
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| Posted: Oct 29, 2020 19:21 Post subject: Re: Unusual bar pyrite from Nanisivik |
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| Hi Bob, Thanks for the reference. The 1995 article in the Min Rec by Pete Richards et al suggests that bars composed of single crystals are usually millimeter sized and the few larger bars that have been observed have a central cavity and are aggregates of several crystals or plates. |
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Jordi Fabre
Overall coordinator of the Forum
Joined: 07 Aug 2006
Posts: 5070
Location: Barcelona
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| Posted: Oct 30, 2020 05:04 Post subject: Re: Unusual bar pyrite from Nanisivik |
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| RussEpp wrote: | | ....The 1995 article in the MinRec by Pete Richards et al suggests... |
In fact that article from the Min. Record is even downloaded here:
https://www.mineral-forum.com/message-board/viewtopic.php?p=19761#19761
I suggest to read the whole thread with the M.R. article, quiet interesting... |
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Philippe Durand
Joined: 10 May 2016
Posts: 653
Location: Normandie
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RussEpp
Joined: 27 Oct 2020
Posts: 14
Location: Manitoba
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| Posted: Oct 31, 2020 09:49 Post subject: Re: Unusual bar pyrite from Nanisivik |
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Some of rectangular fluorites in this 2013 thread are spectacular and seem to be comparable to the Nanisivik specimen as they are elongated cubes as well, at least by appearance. I want to thank everyone for their responses and I would love to see photos of other elongated, striated, cubic pyrites from anywhere. Thanks, Russ |
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