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Tobi
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Joined: 07 Apr 2009
Posts: 4108
Location: Germany
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 Posted: Oct 13, 2015 13:36 Post subject: Strange kind of crystal growth of galena and sphalerite |
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Hi folks,
I recently posted this new specimen of galena and sphalerite on matrix from Rucheng Mine, China: https://www.mineral-forum.com/message-board/viewtopic.php?p=47254#47254
Attached you see a detail photo of a very strange thing I discovered on the backside of the specimen: It looks like a "twinning" between a galena and a sphalerite crystal - what happened here, any clues?
Thanks!
Tobi
| Mineral: | Galena, sphalerite |
| Locality: | | Rucheng Mine, Caojia, Nuanshui, Rucheng, Chenzhou Prefecture, Hunan Province, China |  |
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11378 Time(s) |
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Jesse Fisher
Joined: 18 Mar 2009
Posts: 629
Location: San Francisco
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| Posted: Oct 13, 2015 13:58 Post subject: Re: Strange kind of crystal growth of galena and sphalerite |
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| Two different minerals won't form a "twin." If there is some sort of structural alignment between the galena and the sphalerite it could be an epitaxial overgrowth. If not, then it's just sphalerite partially overgrowing a galena crystal. The galena on the right in the photo looks like a spinel twin, however.
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Pete Richards
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Joined: 29 Dec 2008
Posts: 828
Location: Northeast Ohio
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| Posted: Oct 13, 2015 20:27 Post subject: Re: Strange kind of crystal growth of galena and sphalerite |
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| Jesse Fisher wrote: | | Two different minerals won't form a "twin." If there is some sort of structural alignment between the galena and the sphalerite it could be an epitaxial overgrowth. If not, then it's just sphalerite partially overgrowing a galena crystal. The galena on the right in the photo looks like a spinel twin, however. |
Jesse is right about two-species twinning, and about the twinned galena, according to my eyeball. I think the galena that has the sphalerite intergrowth might also be a twin - the tab on the octahedral face to the lower right might also be a piece of a penetration twin that is otherwise not visible.
I have a specimen from the Nikolaevskiy Mine, Dal'negorsk, that is a somewhat complex intergrowth of galena and sphalerite. The sphalerite has nice sharp octahedral faces, unlike Tobi's specimen, and this helps. The galena is less well-formed however, so as with Tobi's specimen, recognizing a regular relationship between the two species is not easy. But in one direction, there are a bunch of sphalerite crystals in parallel growth with galena that appears to have octahedral faces. This seems to establish that there can be an epitactic relationship between these two isometric minerals, even though they belong to different point group symmetries within the isometric system.
Examination of the rest of the specimen along broken surfaces makes it clear that the sphalerite was the main phase, and that the galena was the later epitactic phase.
I will try to follow with photos....
_________________
Collecting and studying crystals with interesting habits, twinning, and epitaxy |
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Pete Richards
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Joined: 29 Dec 2008
Posts: 828
Location: Northeast Ohio
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| Posted: Oct 14, 2015 09:46 Post subject: Re: Strange kind of crystal growth of galena and sphalerite |
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| Pete Richards wrote: |
... a specimen from the Nikolaevskiy Mine, Dal'negorsk....
....sphalerite was the main phase, and that the galena was the later epitactic phase.
I will try to follow with photos.... |
| Mineral: | Galena epitactic on sphalerite |
| Locality: | | Nikolaevski Mine, Dalnegorsk, Dalnegorsk Urban District, Primorsky Krai, Far-Eastern Region, Russia | |
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| Dimensions: | 6.5 cm wide |
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11122 Time(s) |
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| Mineral: | Galena epitactic on sphalerite |
| Locality: | | Nikolaevski Mine, Dalnegorsk, Dalnegorsk Urban District, Primorsky Krai, Far-Eastern Region, Russia | |
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| Dimensions: | 6.5 cm wide |
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11094 Time(s) |
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| Mineral: | Galena epitactic on sphalerite |
| Locality: | | Nikolaevski Mine, Dalnegorsk, Dalnegorsk Urban District, Primorsky Krai, Far-Eastern Region, Russia | |
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| Dimensions: | 6.5 cm wide |
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11089 Time(s) |
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| Mineral: | Galena epitactic on sphalerite |
| Locality: | | Nikolaevski Mine, Dalnegorsk, Dalnegorsk Urban District, Primorsky Krai, Far-Eastern Region, Russia | |
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| Dimensions: | 6.5 cm wide |
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11134 Time(s) |
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_________________
Collecting and studying crystals with interesting habits, twinning, and epitaxy |
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Tobi
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Joined: 07 Apr 2009
Posts: 4108
Location: Germany
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| Posted: Oct 14, 2015 10:01 Post subject: Re: Strange kind of crystal growth of galena and sphalerite |
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| Thank you for showing this sample, Pete, a very interesting structure. I've seen a lot of galena specimens from Dal'Negorsk, but never such a "coitus" of these two sulfide minerals ;-)
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Xueyan Jin
Joined: 19 Oct 2015
Posts: 11
Location: Jinan
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| Posted: Nov 03, 2015 22:26 Post subject: Re: Strange kind of crystal growth of galena and sphalerite |
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I have a simlar small one~~
| Locality: | | Shuikoushan Mine, Shuikoushan ore field, Changning, Hengyang Prefecture, Hunan Province, China | |
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| Dimensions: | Size: 3.2*4*2cm Weight: 28.6g |
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10605 Time(s) |
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