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Suspicious kobeite.

Posted by Pavel Kartashov  
avatar Suspicious kobeite.
February 18, 2008 03:36AM
ru    
It isn't clear to me, why mineral from the photo [www.mindat.org] with composition "analyses show much Ti, lesser Y,Nb,Th,Nd,Gd,Dy,Er,W,U" named kobeite-(Y)?

Zr is essential constituent of kobeite, and it absent in Austrian mineral. So it is mineral from euxenite group if U>Th (polycrase), or from aeschynite group if Th>U (priorite, blomastrandin). By the way, compare composition of Urstad aeschynite-(Y) on page [www.mindat.org] with Austrian data - we also see Ti>Y>Nb>Th>U...

Colour of the mineral is too light - compare with all other almost black kobeites from the gallery.

All kobeites are obviously prismatic to fibrous, Austrian mineral form isometric grains...

And, of course, kobeite is uncomparable MUCH MORE rare than both euxenite or aeschynite.

Author of the photo should to decide, in which photo gallery is better to move his mineral photo - in aeschynite-(Y) or euxenite-(Y), he has analytical data. But the photo should be eliminated from kobeite gallery.

Kind regards,
Pavel
Re: Suspicious kobeite.
February 18, 2008 11:02AM
at    
Short translaton of
Brandstätter and Niedermayr, 1998 (Neue Mineralfunde):

"Mr. .... discoverd resinous, yellow-brown to orange-brown, prismatic crystals up to 2 mm long. REM-EDS Analysis yielded Ti, Y and O as major components. Powder-XRD gave no result. Only a single-crystal X-ray study with a CCD-Diffractometer allowed the identification of the crystals as kobeite-(Y)."

Further study seems requiered!

Franz Bernhad
avatar Re: Suspicious kobeite.
February 18, 2008 11:55AM
Pavel,
What old references do you have for this mineral. According to the new IMA-list there is no Zr, and the mineral has a euxenite/aeshynite-type formula. I was also looking at the Am. Min. reference given at the Mindat-page it only give a lot of annealing data - no chemistry.
I would appreciate any copies (Pdf) of old original articles, I suppose there is no modern EMP-data?? Or..?

cheers
Johan
avatar Re: Suspicious kobeite.
February 18, 2008 12:13PM
ru    
Dear Franz!

I only repeat again - Zr is ESSENTIAL constituent of kobeite. See [www.mindat.org]

If some mineral give X-ray pattern of thortveitite, but not contain Sc, it can't be thortveitite. It should be gittinsite, or one of keiviites, or something new.

Here is the same situation - mineral with structure kobeite and without Zr is quite another new (or old) mineral.

S.V. Malinko was able to discover turneaureite as long ago as 1961. Instead of this she wrote article "the first occurrence of svabite in USSR". Really it gave XRD of svabite, but didn't contain any fluorine - only Cl. :):):)

Kind regards,
Pavel
avatar Re: Suspicious kobeite.
February 18, 2008 01:03PM
ru    
Johan,
your question only confirm my not high appreciation of the last IMA activity connected with changes in mineral nomenclature. They had splash out baby with water in this case with kobeite.

Wet chemical analyses of kobeites are (1 from Ushio, 2 from Shiraishi):
..............1......2
(Nb,Ta)2O5...2.81...3.87
SiO2.........1.59...1.99
TiO2........26.02..26.21
(Zr,Hf)O2...17.08..14.91 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! This not hog had sneeze! Zr content is higher than in eudialytes! ~1 pfu of Zr! And look also on SiO2 content! It isn't "zircon impurity"!
U3O8.........5.84...5.39
ThO2.........1.31...1.25
Al2O3........0.35...0.33
Fe2O3........9.55*..8.32*
LREE2O3......1.64...1.83
(Y,HREE)2O3.21.98..24.40
MgO..........0.79...0.50
CaO..........0.73...0.53
MnO..........1.48...2.16
H2O-.........0.42...0.47
H2O+.........2.81...3.87
Sum.........99.60..99.41
* total Fe

Ref: Masutomi J., Nagashima K., Kato A. (1961) Mineral. J. Japan, v.3, N3.

What about "modern EMP-data", I am able only to send you again to [www.mindat.org] and [www.mindat.org] I'll try to find my original analytical data. It is not simple for now.

There is something wrong in the last IMA "brain activity" if its result are excludion of calciogadolinite of Nakai from mineral lists and Zr from kobeite formula. :( Of course "apatite-(CaF)" is the great achievement of thought of XX! century!!! :):):) This very remind me Dr. Povarennykh activity in 60th.

Regards
Pavel



Edited 1 time(s). Last edit at 02/18/2008 05:05PM by Pavel Kartashov.
avatar Re: Suspicious kobeite.
February 18, 2008 06:39PM
at    
Pavel,
some days after i updated this picture I got a PM from Alfredo who also was suspicious. I responded to him that I wanted to start a discussion about it.

Here we go.

I`m with you that this micro needs more ID. Exactly THIS micro - I don`t have another one. Although I have been quite busy at that locality in the last year, chances are low to find other stuff in a 20 year abandoned and with trash filled quarry. But lets see; I´ll continue also in this year.
I would suggest and hope that Uwe is willing to do further ID`s?

Regards

Chris Auer
avatar Re: Suspicious kobeite.
February 19, 2008 01:43AM
ru    
If improvement in kobeite-(Y) formula in IMA list wouldn't made, whole billow of "kobeite" finds should waiting us soon. Because of euxenite-(Y) nevertheless is the most abundant niobate in nature after columbites and pyrochlore. And some years later kobeite-(Y) will descredited and become euxenite-(Y) synonim.:(

It would be pity to lost this rare but very interesting mineral on account of stupidity of some IMA functionary. The process had started. Washing out of kobeite term had begin.:(

So your activity, dear Christian, is more harmful for mineralogy than useful. You (and Mr..., mentioned by Franz Bernhad) create objectionable precedent. When/if your "kobeite" will turned out usual euxenite, this able to become argue for descreditation of REAL kobeite. So it would be better to obtain serious analitical data and get to know seriously with literature (not only with textbooks) before. Probably after that your wishing to name usual mineral by name of much more rare one as well as wishing "to start a discussion" will disapear.

Wolframoixiolite was descredited according to the similar absurd reason.

It is interesting for me, is loranskite-(Y) still presents in IMA list? And still with formula YZrTaO6? Exactly this is real scientific fiction, typical mixture (euxenite&zircon in the same bottle). By the way, in the first description of loranskite Nb was predominate over Ta (even in wt.%) and significant Ti amounts were present. How was obtained the present formula of this fictive specie nobody able answer.

It is real secret for me, how this fiction was able to outlast quite REAL mineral - calciogadolinite (should be calciogadolinite-(Y) according to Levinson rule)? On the page [www.mindat.org] loranskite marked as "approwed'!!! By WHOM approved? It was invented in 30th, before WWII!!!

Pavel
avatar Re: Suspicious kobeite.
February 19, 2008 09:52AM
Hi Pavel,
I agree with your doubts about loranskite-(Y). For me it is higly questionable.
In the IMA list it is as valid species with A status [= approved with "special procedure 1987". See American Mineralogist 72 (1987), 1031 (Appendix 2)] with formula (Y,Ce,Ca)(Zr,Ta)2O6. For this reason also in mindat it is as "approved"!. I think that, for the moment, to add a brief description about the doubts is the solution.
Probably Ernie Nickel or Ernst Burke will read this thread and they can add some suggestions.
Ciao. Marco
johan k
Re: Suspicious kobeite.
February 19, 2008 10:48AM
Pavel & Marco,
I had contact with the people responsible for the IMA-list a couple of years ago concerning the issue you are touching upon.
Regarding many of the minerals affected by the Levinson rule they got "approved" (= A-marked) erroneously and "wholesale" because of Appendix 2 in Am. Min,vol 72.
Many of the A species should officialy STILL be only G since only a name-change took place. No new data/investigations was presented.

Ernie Nickel understood the problem/error. But of course the task of going through everything and get all of it right requires a lot of work by someone who is knowledgable and has access to all references.

The solution - as I see it now - no list will never be perfect, so first of all take them all with large pinches of salt. Second, if you know something - publish it. Some of the approved species do not even exist more than in brief publications pre 1950's and they should of course be thrown out, but again it has to be published.

cheers
avatar Re: Suspicious kobeite.
February 19, 2008 11:04AM
Hi Johan K,
the A status for many minerals approved by "special procedure" is not an error; it is a decision (see what Ernie tell about the question in other very recent threads).
I can agree with you that, probably, is not, in same cases, the better decision. Anyway IMA CNMNC (CNMMN at that time) pronounced the opinion of validity about those minerals with the publications of the lists (not only in American Mineralogist but also in some other journals), so officially the A status can also be interpretated as very very correct (also if the species can be considered questionable or not valid).



Edited 1 time(s). Last edit at 02/19/2008 11:19AM by Marco E. Ciriotti.
johan k
Re: Suspicious kobeite.
February 19, 2008 12:49PM
You are sometimes too quick to answer Marco.

I will try and explain so you don't have to fill in any gaps:

1. In American Mineralogist 72 (1987), page 1031 (Appendix 2) had the heading "Revised nomenclature for rare-earth-element minerals" i,e. change in NOMENCLATURE!
2. As pointed ut by Ernie Nickel in another thread special procedures result in A=approval, Rn=renaming and Rd=redefinition.
3. In later IMA-lists (I don't exactly know when it first appeared) the RENAMED minerals in the under point 1 mentioned appendix 2 started to appear as APPROVED with reference to the same appendix.

To start using the said appendix as a reference for approval, you may say "that, probably, is not, in same cases, the better decision" I prefer to just say that this is an error.

I pointed out this to some people in the scientific community and got a kind answer from Ernie Nickel in which he essentially agreed. I do not read to deep into these lists but can see for myself that not too much has been done to correct the errors (at least not the ones I know of).

all best
Re: Suspicious kobeite.
February 27, 2008 08:47PM
at    
The Austrian kobeite-(Y) should be in our collection (Natural History Museum Vienna). Will check.
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