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Dany Mabillard
Joined: 01 Jul 2019
Posts: 352
Location: Valais
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 Posted: Jan 28, 2021 11:30 Post subject: Help needed |
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Hello everybody,
I need some help to confirm or invalidate the following mineral. If you also have a more precise location, I'll be very grateful.
Thanks in advance and keep safe.
Dany.
| Mineral: | Spessartine |
| Locality: | | Tongbei, Yunxiao, Zhangzhou Prefecture, Fujian Province, China |  |
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| Dimensions: | 49 mm x 40 mm x 26 mm |
| Description: |
| For the vendor, it's on Orthoclase but I think is on Microcline. What do you think? |
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13027 Time(s) |
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Volkmar Stingl
Joined: 23 Sep 2012
Posts: 983
Location: Innsbruck
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| Posted: Jan 28, 2021 11:40 Post subject: Re: Help needed |
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Hello Dany,
this is a specimen with smoky quartz, spessartine, and orthoclase from Tongbei, Yunxiao Co., Zhangzhou Prefecture, Fujian Province in China.
Volkmar
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Michael Shaw
Site Admin
Joined: 30 Apr 2008
Posts: 2227
Location: Oklahoma
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| Posted: Jan 28, 2021 13:50 Post subject: Re: Help needed |
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Dany,
As you suggest, the feldspar that that is associated with the Spessartine and Smoky Quartz is Microcline, not Orthoclase. It was originally reported to be Orthoclase, but this has been proven wrong.
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Dany Mabillard
Joined: 01 Jul 2019
Posts: 352
Location: Valais
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| Posted: Jan 29, 2021 11:00 Post subject: Re: Help needed |
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| Volkmar Stingl wrote: | Hello Dany,
this is a specimen with smoky quartz, spessartine, and orthoclase from Tongbei, Yunxiao Co., Zhangzhou Prefecture, Fujian Province in China.
Volkmar |
Thank you for your help. I've checked the location on Mindat and there is this note: The feldspar associated with the spessartine is microcline, not orthoclase as originally reported.
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Dany Mabillard
Joined: 01 Jul 2019
Posts: 352
Location: Valais
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| Posted: Jan 29, 2021 11:26 Post subject: Re: Help needed |
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| Michael Shaw wrote: | Dany,
As you suggest, the feldspar that that is associated with the Spessartine and Smoky Quartz is Microcline, not Orthoclase. It was originally reported to be Orthoclase, but this has been proven wrong. |
Thank you for your help.
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alfredo
Site Admin
Joined: 30 Jan 2008
Posts: 1011
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| Posted: Jan 29, 2021 15:29 Post subject: Re: Help needed |
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| Let's keep in mind that the differences between orthoclase and microcline are so small that they are only kept as separate species because of historical inertia. If they were described as new species nowadays, under current IMA rules, they'd just be a single species. So, in my own collection I label them "K-feldspar" and don't give a hoot which one of them it is, orthoclase or microcline.
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Pete Richards
Site Admin
Joined: 29 Dec 2008
Posts: 842
Location: Northeast Ohio
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| Posted: Jan 29, 2021 16:00 Post subject: Re: Help needed |
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On top of that, orthoclase becomes microcline as it cools down, if it has time. And there is debate about whether there is such a thing as primary microcline - i.e. microcline that did not start out as orthoclase. The transition from orthoclase to microcline leads to a characteristic kind of twinning called cross-hatch or tartan twinning; if it is present the mineral is microcline, but this may require thin sections and microscopy to determine. If it is absent, the mineral could be orthoclase or it still possibly could be microcline - the elusive primary microcline. Probably most if not all k-spar crystals start out as orthoclase, probably most wind up as microcline pseudomorphs after orthoclase.
This ignores sanidine and adularia, other important forms of potassium feldspar. It's complex enough already!
_________________
Collecting and studying crystals with interesting habits, twinning, and epitaxy |
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Dany Mabillard
Joined: 01 Jul 2019
Posts: 352
Location: Valais
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| Posted: Jan 31, 2021 11:34 Post subject: Re: Help needed |
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| alfredo wrote: | | Let's keep in mind that the differences between orthoclase and microcline are so small that they are only kept as separate species because of historical inertia. If they were described as new species nowadays, under current IMA rules, they'd just be a single species. So, in my own collection I label them "K-feldspar" and don't give a hoot which one of them it is, orthoclase or microcline. |
Thank you. I'll use K Feldspar.
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Dany Mabillard
Joined: 01 Jul 2019
Posts: 352
Location: Valais
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| Posted: Jan 31, 2021 11:34 Post subject: Re: Help needed |
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| Pete Richards wrote: | On top of that, orthoclase becomes microcline as it cools down, if it has time. And there is debate about whether there is such a thing as primary microcline - i.e. microcline that did not start out as orthoclase. The transition from orthoclase to microcline leads to a characteristic kind of twinning called cross-hatch or tartan twinning; if it is present the mineral is microcline, but this may require thin sections and microscopy to determine. If it is absent, the mineral could be orthoclase or it still possibly could be microcline - the elusive primary microcline. Probably most if not all k-spar crystals start out as orthoclase, probably most wind up as microcline pseudomorphs after orthoclase.
This ignores sanadine and adularia, other important forms of potassium feldspar. It's complex enough already! |
Thank you for your explanation.
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Dany Mabillard
Joined: 01 Jul 2019
Posts: 352
Location: Valais
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| Posted: Mar 07, 2021 08:22 Post subject: Re: Help needed |
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Hello everybody,
I'd like a confirmation and maybe a more precise location for the following specimen.
Thank you in advance.
Have a great Sunday and keep safe.
| Mineral: | Hematite |
| Locality: | | Switzerland | |
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| Dimensions: | 180 mm x 120 mm x 50 mm |
| Description: |
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| Viewed: |
11758 Time(s) |
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| Mineral: | Hematite |
| Locality: | | Switzerland | |
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| Dimensions: | 10 mm x 5 mm x 2 mm for the biggest one. |
| Description: |
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11773 Time(s) |
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Pete Richards
Site Admin
Joined: 29 Dec 2008
Posts: 842
Location: Northeast Ohio
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| Posted: Mar 07, 2021 08:24 Post subject: Re: Help needed |
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Most likely hematite, but it could be ilmenite as well.
_________________
Collecting and studying crystals with interesting habits, twinning, and epitaxy |
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James Catmur
Site Admin
Joined: 14 Sep 2006
Posts: 1462
Location: Cambridge
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| Posted: Mar 07, 2021 11:27 Post subject: Re: Help needed |
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Do we assume it is Swiss?
| Dany Mabillard wrote: | Hello everybody,
I'd like a confirmation and maybe a more precise location for the following specimen.
Thank you in advance.
Have a great Sunday and keep safe. |
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Sante Celiberti
Joined: 04 Oct 2019
Posts: 699
Location: Tuscany
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| Posted: Mar 07, 2021 11:32 Post subject: Re: Help needed |
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| Pete Richards wrote: | | Most likely hematite, but it could be ilmenite as well. |
Hi, Pete. I sincerely hope you are fine.
I agree with Hematite (ilmenite, present in our Alps with this same shape, is far rarer although possible...).
A warm greeting and stay healthy.
Dany,
if the matrix is a granular adularia, almost surely the specimen comes from Scherbadung area (Monte Cervandone).
Little quartz crystals can accompain the hematite and, often, on the pinacoidal faces of the ditrigonal bipyramids tiny red prismatic crystals of rutile can be in epitaxy.
Hope this helps. Stay safe.
Sante
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Sante Celiberti
Joined: 04 Oct 2019
Posts: 699
Location: Tuscany
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| Posted: Mar 07, 2021 11:45 Post subject: Re: Help needed |
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| James Catmur wrote: | | Do we assume it is Swiss? |
You are right, James!
I assumed it is with too much superficiality... Sorry.
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Dany Mabillard
Joined: 01 Jul 2019
Posts: 352
Location: Valais
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| Posted: Mar 10, 2021 10:15 Post subject: Re: Help needed |
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Hello everybody,
thank you all for your comments. I'll try to get more information about the provenance of the Hematite (at least the country).
Keep safe and have a nice day.
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