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Improving Mindat.orgStrelkinite?

16th Apr 2017 23:47 UTCReiner Mielke Expert

02988120016036339219476.jpg
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:

17th Apr 2017 00:54 UTCPavel Kartashov Manager

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.

17th Apr 2017 01:38 UTCReiner Mielke Expert

03611100016036339213264.jpg
Hello Pavel,


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



and :
02317160015660377019797.jpg



and:
03837810015660377019589.jpg



I could go on as I have about 50 analysis with Na but I think I have made my point.

17th Apr 2017 06:57 UTCŁukasz Kruszewski Expert

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.

17th Apr 2017 13:46 UTCPavel Kartashov Manager

08424410016036339215333.jpg
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

04575700015660377015648.jpg


I haven't under hands of strelkinite spectrum, but this is metanatroautunite one
05320600015660377018590.jpg

17th Apr 2017 14:10 UTCReiner Mielke Expert

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

17th Apr 2017 16:33 UTCPavel Kartashov Manager

Find of carnotite or even curienite, as well as usual autunite at the locality will not surprise me.

17th Apr 2017 18:23 UTCTravis Olds Expert

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

17th Apr 2017 19:15 UTCŁukasz Kruszewski Expert

Very interesting find, Travis! Hoping for a new mineral (-:

21st Apr 2017 09:48 UTCCarsten Slotta 🌟 Expert

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.

21st Apr 2017 13:47 UTCReiner Mielke Expert

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.

21st Apr 2017 16:39 UTCJoy Desor Expert

Uranium minerals cannot be distinguished with EDS well, better XRD if you have sufficient material. If not, Raman helps.


Cheers

21st Apr 2017 18:28 UTCCarsten Slotta 🌟 Expert

According to Dr. Murashko strelkinite is often intergrown with (meta)-tyuyamunite, sometimes also associated with carnotite.
 
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