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Smithsonite from Adis Abeba, Ethiopia??
  
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herrej




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PostPosted: May 05, 2018 13:03    Post subject: Smithsonite from Adis Abeba, Ethiopia??  

This is a nice piece I think but I'm not sure what it is and what is it origin.
It was sold to me as Smithsonite from Adis Abeba, Ethiopia a long time ago.
This seems not correct to me. Can't find anything in books, literature or the internet about Smithsonite at Adis Abeba.
Anyone an idea of the mineral and the origin? The matrix is basalt like.



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Kevin Schofield




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PostPosted: May 05, 2018 14:45    Post subject: Re: Smithsonite from Adis Abeba, Ethiopia??  

herrej wrote:
This is a nice piece I think but I'm not sure what it is and what is it origin.
It was sold to me as Smithsonite from Adis Abeba, Ethiopia a long time ago.
This seems not correct to me. Can't find anything in books, literature or the internet about Smithsonite at Adis Abeba.
Anyone an idea of the mineral and the origin? The matrix is basalt like.


Looks to me suspiciously like "Manufactured, from Somebody's Basement"....

But happy to be demonstrated to be incorrect of course..

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Peter Lemkin




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PostPosted: May 05, 2018 22:22    Post subject: Re: Smithsonite from Adis Abeba, Ethiopia??  

That was my thought too. The 'matrix' looks false [unnatural] and the crystals seem unnaturally attached and of almost exactly the same size and form.......I think you might consider and explore if this is real or not.....sorry to say..... I also have never heard of this mineral from this location....
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Jim Robison




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PostPosted: May 05, 2018 23:19    Post subject: Re: Smithsonite from Adis Abeba, Ethiopia??  

Are you sure this is smithsonite? There is some from Morocco that has this appearance but the crystal size is much smaller in appearance. There is no size given on the piece, but those I have seen from there have fairly small diameter rhomb groups, in the range of 1 cm or so. . Indeed, you can see a shadow underneath the mineral, strongly indicating the white is simply stuck onto the matrix. If the matrix is basalt then calcite would be the potential later mineral, but not in this case. My first reaction was a Romanian calcite, though it would make absolutely no sense to dismantle one of those to construct this rock.
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nicu




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PostPosted: May 06, 2018 00:19    Post subject: Re: Smithsonite from Adis Abeba, Ethiopia??  

The matrix is basaltic, possibly sprinkled with small Olivine crystals. The two dome-like formations seem to be a carbonate mineral but certainly, it is not Smithsonite.
They are man-made attached on the basis. I don't think it would come from Romania....

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alfredo
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PostPosted: May 06, 2018 02:44    Post subject: Re: Smithsonite from Adis Abeba, Ethiopia??  

Another possibility is that the vug was originally lined with a thin layer of saponite, ferrosaponite or other clay-like mineral, which is very common in basalt vugs. Younger minerals like zeolites and calcite grow on top of this clay layer, which is why some basalt vugs get destroyed in ultrasonic cleaners, because the older clay layer desintegrates. It could be the case here, the clay layer partially washed away, leaving that gap between the calcite groups and the matrix. Or it might be glued, like others have said, but not necessarily.

The basalt has an oxidized brownish color, unlike the more normal grey tones. I've collected vuggy brownish basalts like this myself on the highway going West from Addis Abeba, but closer toward Lekemti, although my specimens had heulandite inside rather than calcite, but it could nevertheless easily be from that part of Ethiopia..
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herrej




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PostPosted: May 06, 2018 04:55    Post subject: Re: Smithsonite from Adis Abeba, Ethiopia??  

Thanks you all for the replies. The hemispheres are not glued on the matrix. The lightbreaking/reflections on the photo gives the impressions there is a line between the hemispheres and the matrix but this is an illusion.
The piece is about 3 cm and the cost was $5, so if you want to make a buck with constructing you don't earn a lot. And also unlikely to break a good romanian piece to construct this one.
The matrix is like the Calcite hemispheres you see sometimes from Italian Calcite on basalt, also sometimes brownish.
I think Alfredo's post is the most likely location of the piece and that is is Calcite.
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Gagat Minerals




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PostPosted: May 06, 2018 07:08    Post subject: Re: Smithsonite from Adis Abeba, Ethiopia??  

Peter Lemkin wrote:
The 'matrix' looks false [unnatural] .......


nicu wrote:
The matrix is basaltic, possibly sprinkled with small Olivine crystals. The two dome-like formations seem to be a carbonate mineral....


alfredo wrote:
... the vug was originally lined with a thin layer of saponite, ferrosaponite or other clay-like mineral, which is very common in basalt vugs. Younger minerals like zeolites and calcite grow on top of this clay layer..


in Poland in very similar basalt vugs of Lower Silesia, this other dark minerals coming out of smectite layers are mostly ilmenites - and calcite like this is quite common.
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