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Wanlockhead
  
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James Catmur
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PostPosted: Jul 21, 2020 08:14    Post subject: Wanlockhead  

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.


Wanlockhead, Wytes Cleugh.JPG
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Pete Richards
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PostPosted: Jul 21, 2020 08:31    Post subject: Re: Wanlockhead  

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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Collecting and studying crystals with interesting habits, twinning, and epitaxy
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Riccardo Modanesi




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PostPosted: Jul 21, 2020 08:59    Post subject: Re: Wanlockhead  

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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PostPosted: Jul 21, 2020 09:26    Post subject: Re: Wanlockhead  

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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PostPosted: Jul 27, 2020 07:31    Post subject: Re: Wanlockhead  

Try the fluorescence. It could be Cerussite...
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PostPosted: Jul 27, 2020 08:51    Post subject: Re: Wanlockhead  

There is some fluorescence
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PostPosted: Jul 27, 2020 12:53    Post subject: Re: Wanlockhead  

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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