Scandian ixiolite

Dear friends!
It seems to me, it is necessary to enter scandian ixiolite as variety of ixiolite. Reference is: Knorring O.Sahama T.G., Lehtinen M. (1969) Scandian ixiolit from Mozambique and Madagascar, - Bull. Geol. Soc. Finland, v.41, p. 75-77.
TL for this variety is Naquissupa pegmatite in Alto Ligonja.

I am know, the article exist with description of Sc-ixioite (with ~20 % Sc2O3) from Heftetjern pegmatite in Norway. Unfortunately I haven't it under hands. I am hope, Roy Kristiansen will help us with this reference.

Today I'd analysed ixiolite from Namivu pegmatite. It contain ~8 % Sc and 7% W.
So we have now at least 4 localities for this ixiolite variety.

Kind regards,
Pavel

Hi ,
Yes, Pavel, I will return shortly with more references to both the Heftetjern material and the one from Mozambique. I am away today and tomorrow so I do not have access.
Roy

Here are at least some:

Bergstøl, S. & Juve, G. 1988. Scandian ixiolite, pyrochlore and bazzite in granite pegmatite in Tørdal, Telemark, Norway. Contr. Miner. Petrol., 38:229-243

Raade, G. & Kristiansen, R. 2000a. Mineralogy and geochemistry of the Heftetjern granite pegmatite, Tørdal: a progress report. Skrifter Norsk Bergverkmuseum 17:19-25 (in Eng.)

Wise, M.A., Cerny, P. & Falster, A.U. 1998. Scandium substitution in columbite-groupminerals and ixiolite. Can. Min. 36:673-680

Roy

Dear friends!

I would like to remind about scandian ixiolite category creation.

Today I'd upload the photo of scandian ixiolite [www.mindat.org] with composition (Nb1.21Ta.78Sc.59Fe".49Fe"'.37Ti.25Mn.15W.12Zr.04)4O8 which is close to type specimen of O. von Knorring from Naquissupa pegmatite. It is also Nb-dominant but more poor in Sc content then this.

Kind regards,
Pavel

I would like to emphasize that the material from Mozambique and Madagascar described by von Knorring et al 1969 have much lesser Sc than the scandian ixiolite from Heftetjern.The scandian ixiolite from Mozambique was proclaimed as a new species "scandium ixiolite" by Borisenko et al.1969; this name has no standing.
Borisenko,Maksimova & Kazakova.1969. Scandium ixiolite, a new tantalo-niobate species with formula (A,B)n O 2n. In Dokl.Akad.Nauk.,USSR, Earth Sci.Sect., 189:148-151 (in Russian edition,189(3):619-622).
The Heftetjern material, however, is Sc-dominant, and the Sc-richest (18.8% Sc2O3) has a formula: (Sc1.46 Ta1.16 Nb0.76 Sn0.26 Fe0.24 Mn0.18 Ti0.03)4.09 O8
(Bergstøl & Juve 1988, Wise et al. 1998).Ixiolite ideally has a structure with disordered cations and this could in fact be a new mineral, as pointed out several times by Raade & Kristiansen 2000, Raade et al.2002.It is NOT identical to the new species IMA 2006-056,which is identical to monoclinic synthetic ScTaO4, with a wolframite structure.
While the scandian ixiolite is orthorhombic, but gets monoclinic upon heating, and attains a wolfrmite structure !

Roy

For further discussion of the ixiolite group/varieties consult:
Cerny,P.1989. Mineralogy of Niobium and Tantalum:crystal chemical relationships, paragenetic aspects and their economic implications. In "Lanthanides, Tantalum and Niobium", p.27-79. Eds.Møller,Cerny & Saupe. Springer Verlag,Berlin Heidelberg 1989.

Roy

So we have even two orthorhombic scandian ixiolite group minerals now:
a. Nb-dominant scandian ixiolite from Africa,
b. superscandian ixiolite from Norway.

Systematicaly these minerals are different and has next formulae:
usual ixiolite [(Ta,Nb,Ti)2(Fe,Sn,Mn)2]4O8
Sc-ixiolite from Africa [(Nb,Ta,Ti)2(Sc,Fe,Mn)2]4O8
superscandian ixiolite [(Ta,Nb,Ti)2(Sc,Sn,Fe)2]4O8

And will someone insert these ixiolite "varieties" in the database at last? Or here only varieties similar to "opalised glass" or "onyx marble" are needed? And opalised onyx shit of course... :(

Pavel

Knorring's Sc ixiolite formula was (Nb1.01Ta.85Ti.56Sc.53Fe".34Fe"'.34Sn.20Mn.10)4O8.

Ok. rereading this, I'm going to add two new entries.

Jolyon



Edited 1 time(s). Last edit at 08/10/2007 10:57AM by Jolyon Ralph.

I have added items for these two. Once we have more data on these possible species/varieties they can be updated.

Jolyon

Certain.......I think that my representation and of Rui Nunes it is included in this article. I think that the samples are from the same mine.

Thank your Jolyon,
it seems to me, that [www.mindat.org] is better to name "scandian ixiolite (of Knorring)", and [www.mindat.org] - "scandian ixiolite (of Bergstol). They aren't unnamed sensu stricto. Both should be reflected on ixiolite page as varieties.

Dear Martins,
your [www.mindat.org] is very similar to scandian ixiolite from Naquissupa pegmatite from my collection. My specimen is intergrowth of two half-balls and is too large to be photographed through microscope. Other your specimens and Rui one more similar to Namivu material. It would be great to check their composition.

Pavel

Ok - changes made.

Jolyon

Thank you , once more!

Pavel

according to The Mineralogical Record, vol 31, nº 6, the specimens of scandian-ixiolite described by von Knorring et al are from Naquissupa pegmatite. This includes several mines: Muiane, Naipa, Maridge, Nihire. I've no references for Namivu pegmatite.

Pavel, when you answer to the other portuguese, I understood (maybe I'm wrong) that you say the composition of Namivu and Naquissupa ixiolites could be different. You make me think:

- if their composition are really different,and if von Knorring used specimens from Naquissupa, then a specimen from Namivu could not be a scandian-ixiolite (of von Knorring)?;

- my specimens, that I though they come from Naquissupa, are almost like the one you say come from Namivu. Are you shure about Namivu pegmatite existence? Maybe a new quarry?

Thank you

Jorge

Von Knorring (1969) describes and analyzes 4 samples of what he calls "scandian ixiolite" from 4 different localities.
These localities are:
1. From Muiane pegmatite mine, Mozambique 6.oo % Sc2O3
2. Naquissupa pegmatite (collected at the Muiane mine's sorting factory but said to come from the Naquissupa pegmatite in the neighborhood ) 7,50 % Sc2O3
3. From one of the pegmatites in the Antsirabe area, Madagascar 2,10 % Sc2O3
4. From Betanimena pegmatite, madagascar 5,10 % Sc2O3

Dear Jorge,
Namivu is rather old locality. See: Gomes Figueiredo C.S. (1967) Alteration of spodumene and lepidolite with formation of dioctahedral chlorite plus dioctahedral montmorillonite interstratifications with dioctahedral chlorite, - Mem. et Notic. Miner. Univer. Coimbra, v.64, p. 32-57. Description of tosudite from Namivu pegmatite.

Compositions of Namivu and Naquissupa ixiolites is really slightly different, as you can see from given above formulae. Main difference is in Sn and Ti contents. But in main features their compositions are similar - Nb-predominance, Fe>>Mn, Sc>Fe">Fe"'>Mn etc. And sc-ixiolite from Namivu is exactly scandian ixiolite of Knorring. Scandian ixiolite of Bergstol is the another Ta-dominant mineral.

Regards,
Pavel

Hello Pavel and Knut

Ok, undestood.

So, if I want to be shure about my specimens pegmatite's origin, I should make a chimical analysis, wouldn't you say so?

Thanks

Jorge

Dear Jorge,
I am afraid, that without analytical data it would impssible to classify your ixiolite specimen.

Some minerals are too hard to recognize or to distinguish by eye. For example, only unexpirienced collector will labeled such specimen [www.mindat.org] as eudialyte. More prudent collector will say - this is mineral of eudialyte group, analysis is necessary for more exact determination. And really, on this photo we see kentbrooksite from absolutely another locality, then photos author stated (this is Lovchorrite mine - compare with [www.mindat.org] ).

So if you want to be really SURE about your specimens,you SHOULD to make a chimical analysis of them as minimum. XRD investigation also is very desirable.

Regards,
Pavel

Dear Pavel

You know, I absolutely agree with you. My great difficulty is to label some specimens.

In Portugal it's not easy to get analytical daterminations. And even when you use the Mindat photos to compare, and it is a great help no doubt about it, you can´t be 100% shure because most minerals appears in so great number of forms,shapes and colors that makes very difficult to be certain. Collecting minerals it's not like collecting stamps.

Besides that, at least for the portuguese labels for portuguese mineral photos you can´t take them seriously. Unfortunately, they have no cientific basis. If you look the 'detailed' field on same portuguese mine, you'll understand what I mean - someone just remenbered to call to its specimen 'mineral xx' or mineral yy'. Maybe that way they can say they have a huge collection, I don't know. You see photos of specimens that look alike, but you see they have different names.

When you tell me that even professionals can get you wrong (and I mean not as purpose) because they don´t do they job work, it means that it's almost impossible for small collectors, like me, to be shure about what they have.

Thanks for you help and kindness

Jorge