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Dioptase
  
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herrej




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PostPosted: Dec 19, 2017 16:30    Post subject: Dioptase  

Also on a small show in Holland I bought this Dioptase. It's like a geode with a lot of Dioptase crystals and on top of some crystals some small Calcite crystals.
The reliable German dealer said it was from Tsumeb and from the upper levels on the mine.
The piece looks different from other pieces of Tsumeb, more like Kaokoveld, but he assured me this was Tsumeb. He got it from an old collection in Germany, from which Namibia was a colony in the end of the 1800's and the beginning of the 1900's.
Did anyone see something like that from Tsumeb before?



P1010328.JPG
 Mineral: Dioptase
 Locality:
Tsumeb Mine, Tsumeb, Otjikoto Region, Namibia
 Dimensions: 5.5x4x2.5cm
 Description:
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P1010328.JPG


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bob kerr




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PostPosted: Dec 19, 2017 20:30    Post subject: Re: Dioptase  

show the back - the matrix is most important to determining location.
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Debbie Woolf




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PostPosted: Dec 19, 2017 21:26    Post subject: Re: Dioptase  

I do not think it is a Tsumeb specimen, I have seen similar specimens and they were from Guchab, Otavi, which was mined 1908-1911 and 1924-1927. There is also uncertainty whether dioptase was found in the upper levels at Tsumeb. Either way it's a lovely specimen.
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Pierre Joubert




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PostPosted: Dec 20, 2017 01:32    Post subject: Re: Dioptase  

bob kerr wrote:
show the back - the matrix is most important to determining location.


Nice specimen. The Tsumeb dioptase is usually associated with calcite, while the Kaokoland dioptase usually has shattuckite/plancheite with it.

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Jordi Fabre
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PostPosted: Dec 20, 2017 04:56    Post subject: Re: Dioptase  

Malcolm Southwood wrote:
I'd be a little reluctant to comment on the origin of your specimen based on one rather indistinct photograph, but one thing I can tell you is that it is not from the "upper levels" at Tsumeb. Dioptase was extremely rare in the first oxidation zone - so rare, in fact, that it is legitimate to question whether or not it even occurred in the "upper levels". Pre-WWII specimens of dioptase attributed to Tsumeb invariably turn out to be from the nearby Guchab-Rodgerberg mines.
By far the majority of Tsumeb dioptase was recovered from between 30 and 32 levels in the second oxidation zone, and a much smaller quantity from deeper still in the third oxidation zone.
(See: http://www.tsumeb.com/en/minerals/488/dioptase/
link normalized by FMF )

Hope this helps

Mal

Hi Mal, to know how to publish links in FMF please check: Links within the message forum
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herrej




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PostPosted: Dec 20, 2017 13:14    Post subject: Re: Dioptase  

Bob, Debbie, Pierre and Malcolm,

Thanks for your reactions. When looking in my archive of mineral books I think Guchab is the best guess for the specimen. Here a picture of the backside, it's Plancheite like I think. I did see in an article that Plancheite with Dioptase was a combination found in Guchab, not in Tsumeb.
I think the small crystals on the Dioptase then would be Quartz and not Calcite. It's a bit bubbly almost chalcedony like. And that doesn't sound like Calcite. And I never heard of Dioptase with Hyalite.

So do you agree with me that the most likely mine is Guchab and the piece is Quartz on Dioptase with a Plancheite matrix?

I think we can rule out Kaokoveld because the combination of Dioptase and Quartz and the old origin of the piece.
And like Malcolm said, old pieces of Guchab were sold as Tsumeb.

Regards and already happy with your replies.

Harry



P1010334.JPG
 Mineral: Dioptase
 Locality:
Tsumeb Mine, Tsumeb, Otjikoto Region, Namibia
 Description:
 Viewed:  2352 Time(s)

P1010334.JPG


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Pierre Joubert




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PostPosted: Dec 20, 2017 14:19    Post subject: Re: Dioptase  

herrej wrote:
Bob, Debbie, Pierre and Malcolm,

Thanks for your reactions. When looking in my archive of mineral books I think Guchab is the best guess for the specimen. Here a picture of the backside, it's Plancheite like I think. I did see in an article that Plancheite with Dioptase was a combination found in Guchab, not in Tsumeb.
I think the small crystals on the Dioptase then would be Quartz and not Calcite. It's a bit bubbly almost chalcedony like. And that doesn't sound like Calcite. And I never heard of Dioptase with Hyalite.

So do you agree with me that the most likely mine is Guchab and the piece is Quartz on Dioptase with a Plancheite matrix?

I think we can rule out Kaokoveld because the combination of Dioptase and Quartz and the old origin of the piece.
And like Malcolm said, old pieces of Guchab were sold as Tsumeb.

Regards and already happy with your replies.

Harry


What concerns me is this note from Mindat: 'Guchab was mined between 1908-1911 and Rodgerberg from 1924-1927. Note: dioptase specimens from here are indistinguishable from Tsumeb dioptase.'

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