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James Catmur
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Joined: 14 Sep 2006
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Location: Cambridge
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 Posted: Jul 21, 2020 08:14 Post subject: Wanlockhead |
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My son picked this up in Whytes Cleuch at it looked unusual and we only noticed this pocket when we got home. It is not Calcite (I did a test with acid), so I wonder what it is. The rock it is in is Baryte and Goethite and it is clear that the pocket was left when a mineral was dissolved.
| Mineral: | Unknown |
| Dimensions: | FOV is 1 cm |
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Pete Richards
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Joined: 29 Dec 2008
Posts: 828
Location: Northeast Ohio
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| Posted: Jul 21, 2020 08:31 Post subject: Re: Wanlockhead |
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James, I trust your observations completely, but it sure looks like calcite, down to the inclined cleavage shown by several of the crystals. Perhaps try the acid again, warmed, on a powder made from one of the crystals.
The other possibility that occurs to me is that it is barite. It also has an inclined cleavage in a pair of directions. It definitely will not fizz with acid!
If you can see it well enough, the cross-sectional shape should distinguish between calcite (triangular, trigonal symmetry) and barite (rectangular, orthorhombic symmetry), as should the number of inclined cleavages (calcite - three of the same kind; barite - two of the same kind plus a third in a different orientation).
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| Your photo, marked to show apparent cleavage planes. |
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Collecting and studying crystals with interesting habits, twinning, and epitaxy |
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Riccardo Modanesi
Joined: 07 Nov 2011
Posts: 618
Location: Milano
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| Posted: Jul 21, 2020 08:59 Post subject: Re: Wanlockhead |
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Hi to everybody!
What about celestine? It's another possibility!
Greetings from Italy by Riccardo.
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Hi! I'm a collector of minerals since 1973 and a gemmologist. On Summer I always visit mines and quarries all over Europe looking for minerals! Ok, there is time to tell you much much more! Greetings from Italy by Riccardo. |
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James Catmur
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Joined: 14 Sep 2006
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Location: Cambridge
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| Posted: Jul 21, 2020 09:26 Post subject: Re: Wanlockhead |
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Thanks Pete.
Calcite was my first thought, hence doing the test. Given that the matrix is Baryte, I did wonder about Baryte and I now suspect it is Baryte. Based on your suggestion I found a crystal in one of the pockets that has cleaved and Baryte looks right.
Riccardo - Celestine has not been identified there (so far)
James
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Jordi Fabre
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Location: Barcelona
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| Posted: Jul 27, 2020 07:31 Post subject: Re: Wanlockhead |
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| Try the fluorescence. It could be Cerussite...
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James Catmur
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Joined: 14 Sep 2006
Posts: 1343
Location: Cambridge
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| Posted: Jul 27, 2020 08:51 Post subject: Re: Wanlockhead |
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| There is some fluorescence
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Jordi Fabre
Overall coordinator of the Forum
Joined: 07 Aug 2006
Posts: 4894
Location: Barcelona
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| Posted: Jul 27, 2020 12:53 Post subject: Re: Wanlockhead |
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| James Catmur wrote: | | There is some fluorescence |
Why not then? Cerussite is very sensitive to the water and frequently shows this rounded appearance due to partial dissolutions.
Put a small parcel inside HCl 10% or similar and if finally dissolves, but much slower than the Calcite, then you have good chances that it could be Cerussite.
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