Quick Links : Mindat手册 The Rock H. Currier Digital Library Mindat Newsletter [Free Download]

主页关于 Mindat Mindat手册 Mindat的历史版权 Who We Are 联系我们于 Mindat.org刊登广告

捐赠给 Mindat Corporate Sponsorship 赞助板页已赞助的板页在 Mindat刊登广告的广告商于 Mindat.org刊登广告

Learning Center What is a mineral?The most common minerals on earth Information for Educators Mindat Articles The Elements The Rock H. Currier Digital Library Geologic Time

搜索矿物的性质搜索矿物的化学 Advanced Locality Search 随意显示任何一种矿物 Random Locality 使用minID搜索邻近产地 Search Articles 搜索词汇表更多搜索选项

Mindat手册添加新照片 Rate Photos 产区编辑报告 Coordinate Completion Report 添加词汇表项目

Mining Companies 统计会员列表 Mineral Museums Clubs & Organizations 矿物展及活动 The Mindat目录表设备设置 The Mineral Quiz

照片搜索 Photo Galleries Search by Color 今天最新的照片昨天最新的照片用户照片相集过去每日精选照片相集 Photography

Discussions

💬 Home 🔎 Search 📅 Latest

╳Discussions

💬 Home 🔎 Search 📅 Latest

Groups

Recent Images in Discussions

MineralsSamarskite-(Yb)

28th Jun 2019 15:34 UTCJohan Kjellman Expert

A recent entry under formula says:

"by analogy to samarskite-(Y) Fe is now included as a separate cation; this relates to the structure refinement, of samarskite-(Y), by Britvin et al.( 2019, in press); Fe was formerly reported one of the elements substituting for Y".

Britvin et al. 2019 do not present any data to support this. The results of the paper concern only one metamict sample from the type locality of samarskite-(Y) and one crystalline sample of what they call samarskite-(Y) from Eifel.

The only evaluation of samarskite-(Yb) with respect to the ordered formula that I know of was done by me in 2017 -

https://www.researchgate.net/publication/322147711_ABC2O8_-_a_new_look_on_the_crystal_chemistry_and_classification_of_samarskite_group_minerals

- wherein I conclude from evaluating more than 1000 analyses of samarskite related minerals:

"(a) Primary S[amarskite]G[roup]M[inerals] (Q4) ought to be described by an ordered formula, (Y*,U*,Ca)(Fe3+,Fe2+,Ti)(Nb,Ta,W)₂O₈, with an A-site occupied by large cations analogous to those in M’-fergusonite and euxenite...(f) the data suggests that several species are questionable, e.g. calciosamarskite and samarskite-(Yb), of which the quality is too low (Q2-Q0) and does not fit the ABC₂O₈-formula."

Rephrased and more to the point: yttrotantalite-(Y), samarskite-(Y) and ishikawaite are conformable with the suggested AMB₂O₈ formula, calciosamarskite and samarskite-(Yb) are not.

28th Jun 2019 21:34 UTCŁukasz Kruszewski Expert

Hi Johann. Thanks for this notice. I've added this formula note as soon as the samarskite-(Y) formula was modified to have Fe as an essential constituent. I will switch the original formula back.

I may add your notes on calciosamarskite and samarskite-(Yb) if you want. But as soon as there is no discreditation proposal, I don't think we may change anything. If samarskite-(Yb) turns out to be true then I suppose it should be the exactly Yb-dominant analogue of samarskite-(Y) (and calciosamarskite the Ca-dominant one of both).

28th Jun 2019 21:42 UTCŁukasz Kruszewski Expert

OK, I've changed the samarskite-(Yb) page and added your paper's reference to this site, and to samarskite-(Y) and calciosamarskite pages.

Thanks!

Luke

28th Jun 2019 23:21 UTCJohan Kjellman Expert

Thanks, grateful for this!

Exactly my point, no changes without substantial data to support them. My paper concerns all the mentioned minerals, but according to my observations the AMB2O8 ordering has only been observed in sam-(Y), ishikawaite and yttrotantalite.

By the way, the general formula before the change ought to have been written ABO4, or for comparison A2B2O8, for all these minerals. I say that because now, after you changed it back, the samarskite-(Yb) has mistakenly become AB2O8.

cheers

28th Jun 2019 23:50 UTCJohan Kjellman Expert

Another thing, the "samarskite group" has never been formally characterized, these days I prefer to talk of "samarskite related minerals".

I took note of this as I see in the Mindat-list of the "group" srilankite, ZrTi2O6, which does neither order ABO4 nor AMB2O8. It does also not contain any large cations that typically goes into the A-site. In my thinking srilankite is more closer to ixiolite structures.

cheers

4th Jul 2019 10:00 UTCJohan Kjellman Expert

Luke,

When you changed the samarskite-(Yb) formula back to the simplified original one it did not come out right, on any of the pages.

You wrote:

(Yb,Y,U,Th,Ca,Fe)(Nb,Ta)2O8

Simmons et al. 2006 write:

(Yb,Y,REE,U,Th,Ca,Fe2+)(Nb,Ta,Ti)O4

cheers

8th Aug 2019 20:28 UTCFrank K. Mazdab 🌟 Manager

Hi Johan... here's a test reply to help you find this thread.

9th Aug 2019 01:19 UTCHarold Moritz 🌟 Expert

Glad you found this thread, I had sent a link to it a few weeks ago to some friends who have done some work on samarskite and now I can send the link to this "new" version, and also I wanted to see what comes up after my name in these new posts! (I hope it is something good).

9th Aug 2019 09:32 UTCJohan Kjellman Expert

Fine , I am back.

The samarskite-(Yb) formula on the samarskite-(Yb) page still needs to be changed back to that originally published by Simmons et al. 2006, i.e.

(Yb,Y,REE,U,Th,Ca,Fe2+)(Nb,Ta,Ti)O4

14th Aug 2019 15:52 UTCUwe Kolitsch Manager

The IMA list simply uses

YbNbO4

14th Aug 2019 19:00 UTCFrank K. Mazdab 🌟 Manager

Yes, I think I recall a thread from a few weeks ago where it was mentioned that the IMA was moving away from having end-member formulas with commas in them, and if so, I applaud the effort.

You can't write any exchange vectors with that Simmon et al 2006 mess. Formulas like that are fine to illustrate the complexity of substitutions, but having one simplified formula for balancing reactions seems logical. If a minor constituent actually turns out to be essential (like the 1/4 K occupancy of the alkali site in nepheline), then the formula should be re-written to accommodate such observations; otherwise, we should follow the advice uttered by every hippie portrayed in a 1960s movie, "simplify, man!"

14th Aug 2019 22:42 UTCJohan Kjellman Expert

Frank,

with some vivid imagination you could, but I prefer pure end member style. I just quoted Simmons et al since I did not know what it was before Luke changed it, but maybe you as managers can see that in the Edit log. In any case, it needs a change, as it stands now the formula is off.

cheers

15th Aug 2019 01:27 UTCFrank K. Mazdab 🌟 Manager

So is the preferred formula

YbNbO₄

YbFe³⁺Nb₂O₈

15th Aug 2019 13:17 UTCJohan Kjellman Expert

YbNbO4

Frank and others I was just posting a lengthy answer but it just came out awful in this new system so I had to delete it.

How to format the text directly?

In cutting and pasting formatted text, the italics, sub- and superscripts, etc. are deleted as well as the rows and paragraphs.

cheers

15th Aug 2019 13:24 UTCJohan Kjellman Expert

Here we go (at least I could enter rows and paragraphs)

I don’t know what Mindat’s official policy is but firstly there is no officially IMA-approved ”samarskite group”. However, there has been an understanding from the very beginning – 1839 – by researchers of ”these minerals” that they are related. Uranotantal the original name of samarskite (with high U-content) was made in allusion to yttrotantal, the earliest discovered mineral of the ”group”.

Also bear in mind, that this was in the time when there was a controversy regarding columbium and tantalum, as the dual identites of these elements was not resolved. It was rather a name controversy over one element where the ”Swedish-German school” were loyal to tantalum, hence yttrotantal(ite) and uranotantal, and the ”Anglo-american school” advocated columbium, hence yttrocolumbite. The definite identification of the two elements was not until 1846 by Heinrich Rose, who gave the new name niobium to columbium. (The formal agreement of the present chemical nomenclature, i.e. niobium and tantalum, was if I remember rightly not settled until mid 20th c. in favour of the Swedish-Germans, however at the ”cost” of the German word wolfram, which was replaced by tungsten which was used by the English and Americans. The fun part of this agreement is that tung sten is from the Swedish words for heavy stone.)

(attached you find a table of historic nomenclature presented at PEG2017, which displays my standing and recommendations regarding the names and status of the minerals)

These were the standing IMA formulas in mid 2017:

yttrotantalite-(Y), (Y,U,Fe2+)(Ta,Nb)(O,OH)4

samarskite-(Y), (Y,Ce,U,Fe,Nb)(Nb,Ta,Ti)O4

ishikawaite, (U,Fe,Y)NbO4

calciosamarskite, (Ca,Fe,Y)(Nb,Ta,Ti)O4

samarskite-(Yb), YbNbO4

Based on an evaluation of more than 1000 microprobe analyses from several researchers, I (Kjellman, 2017) suggested that the ordered formula (Y*,U*,Ca)(Fe3+,Fe2+,Ti)(Nb,Ta,W)2O8 was applicable to the following confirmed endmembers:

yttrotantalite-(Y) YFeTa2O8 i.e. YFe3+Ta2O8

samarskite-(Y) YFeNb2O8 i.e. YFe3+Nb2O8

ishikawaite UFeNb2O8 i.e. UFe2+Nb2O8

in october 2018 IMA/CNMNC approved

ekebergite ThFeNb2O8 i.e. ThFe2+Nb2O8

in december 2018 IMA/CNMNC accepted the redefinition of

samarskite YFe3+Nb2O8

The latter two appear in the IMA/CNMNC list from July 2019, whereas the formulas of the other related minerals are identical to those from 2017.

cheers

15th Aug 2019 19:46 UTCFrank K. Mazdab 🌟 Manager

Hi Johan,

It seems counterintuitive that if samarskite-(Y) is YFe³⁺Nb₂O₈ , that samarskite-(Yb) wouldn't be YbFe³⁺Nb₂O₈ . It seems the nomenclature should be changed; maybe someone *should* recommend defining a group name that covers some of the related(?) minerals in your table.

By the way, as an aside for adding mineral formulas (now that I sort of got it to work) to avoid the obnoxiousness of losing formatting and editing abilities when cutting and pasting, is that I've picked a "go-to" formula (in this case, the one for samarskite-(Y)), inserted it, and then carefully modified it (here adding a "b" after the "Y") and carefully changing any subscripts as necessary (here no changes were necessary). I just re-insert it where ever I need it, and modify it accordingly. Terrible way to do it, but at least it gives me some formula editing flexibility. My general "go-to" formula has so far been epidote, because it's long and has both superscipts and subscripts. I'll eventually look for an even longer one with more superscripts to give me more flexibility, or alternatively, I'm seriously hoping Jolyon with return our formatting buttons!

15th Aug 2019 23:22 UTCJohan Kjellman Expert

The issue is how mindat chose to report on extant data. I just delivered a lot of condensed information, now it's up to you guys.

cheers

22nd Nov 2021 00:48 UTCOwen Missen

Hi everyone,

I note that there has been plenty of previous discussion on yttrotantalite-(Y).

There remains an error in the formula for the mineral yttrotantalite-(Y); YFe³⁺(Ta,Nb)62O₈ appears to lack a subscript, though '62' cannot be correct. Perhaps

YFe³⁺(Ta,Nb)₂O₈ was intended based on the YFe³⁺Ta₂O₈of (Kjellman, 2017) as described above?

Thanks!

Go to top of page