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Strelkinite?

Posted by Reiner Mielke  
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Reiner Mielke April 16, 2017 11:47PM
https://www.mindat.org/photo-571197.html I recently had some of this analyzed and it came back metatyuyamunite not strelkinite ( not trace of Na). See analysis:

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Pavel Kartashov April 17, 2017 12:54AM
This equipment (with low sensitivity for Na) don't fit for such material. From your spectrum we can state only that the mineral contains much less Ca than normal tyuyamunite. I had check such material from M. Murashko myself - it is full of Na.
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Reiner Mielke April 17, 2017 01:38AM
Hello Pavel,

Like I have stated before the system does detect Na, for example:


and :


and:


I could go on as I have about 50 analysis with Na but I think I have made my point.
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Łukasz Kruszewski April 17, 2017 06:57AM
It could be metatyuyamunite, although the Ca seems a little bit too low to me (but I suppose it is "mixed" with U line); also, there seems to be some Fe (or Mn) in it, with some Al also present.



Edited 2 time(s). Last edit at 04/17/2017 06:58AM by Łukasz Kruszewski.
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Pavel Kartashov April 17, 2017 01:46PM
The presence of tyuyamunite does not negate the possibility of having strelkinite in the same sample. It is quite usual situation - coexistence of two-three or more uranium micas together and their mutual intergrowths and overgrowths. Moreover due to geochemistry of host rocks, tyuyamunite must to be and is more abundant than strelkinite formation of which ruled by groundwaters movements.
so you had prove only the fact, that strelkinite is absent in your samples. But, of course, presence of such rare species in samples should to be confirmed by some method and you quite may be right in case of mentioned photo. My strelkinite from M. Murashko looks some different (not so nice as at the photo).

When I speak about sensitivity, I mean such spectra


I haven't under hands of strelkinite spectrum, but this is metanatroautunite one

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Reiner Mielke April 17, 2017 02:10PM
Hello Pavel,

"so you had prove only the fact, that strelkinite is absent in your samples." exactly my point. In otherwords what I was saying is that without analysis one cannot say it is strelkinite as it could be tyuyamunite so the photos posted are questionable and could mislead people into thinking their tyuyamunite samples are strelkinite. As for my sample being tyuyamunite, you are correct, the analysis are not good enough to confirm that. I just assumed it was metatyuyamunite since the only two U,V minerals found at that locality are strelkinite and metatyuyamunite https://www.mindat.org/loc-31332.html
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Pavel Kartashov April 17, 2017 04:33PM
Find of carnotite or even curienite, as well as usual autunite at the locality will not surprise me.
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Travis Olds April 17, 2017 06:23PM
Just last week I attempted single xl XRD on some Jordan material and consistently got the carnotite group cell w/ halved c.. Albeit the diffraction was very poor, and reflections doubling c to give the reported strelkinite cell (from PXRD) may have been just very weak... so in the absence of chemistry this means little. I will try probing the material and get back to you.

But I agree with Pavel, intergrowth between uranyl vanadates is incredibly common. For example we've recently found Sr-dominant francevillite group xls growing intimately on carnotite.

Travis
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Łukasz Kruszewski April 17, 2017 07:15PM
Very interesting find, Travis! Hoping for a new mineral (-:
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Carsten Slotta April 21, 2017 09:48AM
Hi All,

this find has been properly analyzed by Dr. Murashko. As mentioned by Pavel the chemistry of these uranium micas can differ

from crystal to crystal, so if you would take xls from different spots of the sample and analyze them I assume you will get different

results. Just because you have found no Na in your particular crystal it doesn’t necessarily mean it can’t be elsewhere on the

specimen.
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Reiner Mielke April 21, 2017 01:47PM
Hello Cartsen,

This may be correct but that fact should be stated in the descriptions as this situation does not hold true for all species from that group.
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Joy Desor April 21, 2017 04:39PM
Uranium minerals cannot be distinguished with EDS well, better XRD if you have sufficient material. If not, Raman helps.

Cheers
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Carsten Slotta April 21, 2017 06:28PM
According to Dr. Murashko strelkinite is often intergrown with (meta)-tyuyamunite, sometimes also associated with carnotite.
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