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Mineralogical ClassificationStatus of stibiconite

6th Sep 2014 00:44 UTCNorman King 🌟 Expert

Stibiconite is a secondary mineral reported from many localities that include antimony minerals, especially stibnite. It is said to be a variety of the roméite group, rather than a mineral in its own right. But I thought that a mineral group would include mineral species, and those might then be subdivided into varieties (rather than going directly from group name to a varietal name). The list of minerals within the roméite group on the Mindat page does not include stibiconite as a member of the group. I don’t get it. Is stibiconite a member of the group, or not. And how can it be a variety of the group, without also being a variety of one of the minerals that make up the group?

6th Sep 2014 02:11 UTCAlfredo Petrov Manager

"Variety" was the wrong word to use in the description. Any given specimen of stibiconite has to be one of the half dozen accepted romeite group members, or a new member species, or a mixture. The problem is that few stibiconites have been suffiently studied to know which of the above is the case for any given locality. So the best we can say is "member of the romeite group". I would suggest changing the word "variety" to "member".

6th Sep 2014 02:30 UTCReiner Mielke Expert

Yes that makes much more sense. Have any of the stibiconites been analyzed?

6th Sep 2014 12:05 UTCNorman King 🌟 Expert

So far I have one powder XRD analysis of an antimony oxide from Lookout Pass. It simply forms a mesh of crystals when replacing parapierrotite, without the expected radial habit that results from replacement of stibnite, so I didn't know what to expect. The mineral we found is hydroxycalcioroméite (lewisite is a synonym). Generally I have simply been referring to "antimony oxides." I don't know what other "stibiconites" might be out there, so I guess we should keep the reference to stibiconite, and add hydroxycalcioroméite to the Lookout Pass mineral list.

EDS tests show at least one other pure antimony oxide (I mean without Ca, Fe, Na, etc., but with plenty of oxygen), possibly only because hydrogen isn't picked up by the analysis to determine if water is present. We are calling that sénarmontite if in octahedrons, but otherwise it may be either valentinite or cervantite in absence of data more discriminating than that supplied by EDS. I hope to get enough powder of that material to distinguish which it is.

I infer that all (former) stibiconite should be recognized as one of the newer minerals that has something other than antimony as major cation(s). If stibiconite is still a valid mineral, it should be listed as a member of the roméite group, right? Maybe there should be quotation marks around "stibiconite," rather than saying it is a member of the roméite group, because it seems it is no longer a member of that group (and maybe not even a valid mineral, or is it?).

18th Sep 2014 16:02 UTCDaniel Atencio

Dear Norman,

Please read:

http://pubsites.uws.edu.au/ima-cnmnc/Atencio%20et%20al%20pyrochlore%20nomenclature.pdf

Regards,

Daniel.

24th Sep 2014 16:48 UTCNorman King 🌟 Expert

I have to revisit this because the issue does not seem to have been resolved, and we have verified by XRD that stibiconite occurs at Lookout Pass, in addition to hydroxycalcioroméite that we reported earlier. Compositions and modes of occurrence for these materials from Lookout Pass are different. The stibiconite may have the ideal formula of Sb⁺³Sb⁺⁵₂O₆(OH), and I suspect the same material occurs in many other places world-wide. There seems to be nothing else in it but Sb, O, and water (also using data from EDS). Obviously, there is something "out there" that has been called stibiconite and it produces this particular XRD pattern that is on file.

The above formula is from webmineral.com, Mineralienatlas.de, and Handbook of Mineralogy, all of which still list stibiconite as a mineral. I understand that stibiconite has been discredited, however (thank you for the copy, Daniel!). But nothing has been put in its place for the roméite group mineral that is purely antimony hydroxide, with Sb⁺³ at the A site and Sb⁺⁵ at the B site. Presumably, a mineral that would be named stibioroméite (listed hypothetically in other sources such as Mineralienatlas) will ultimately be established. Or perhaps hydroxystibioroméite.

Where do the known “stibio” materials belong in the mean time? Why do we not keep stibiconite until someone acquires enough analytical data to redo the nomenclature based upon the system put forth by Atencio et al (2010), instead of suggesting the mineral is not valid? We know it exists, and nothing needs to be established here–we already have stibiconite. Maybe we should simply say that the name needs to be changed, rather than that the mineral is not valid, that it doesn’t exist, or that it has not been verified. Perhaps when we have more analyses of things now listed as stibiconite, we will know what they actually are, and those that do not have the correct composition and structure can be re-labeled and moved to the correct gallery. But the earlier sloppy work does not necessarily reflect on the validity of the species stibiconite as it has been recognized.

What am I missing here?

24th Sep 2014 18:06 UTCAlfredo Petrov Manager

What we have done in several similar cases elsewhere in the database is list the old name and the person making the original description, like: "Stibiconite (of Blum and Delffs)", or whoever the original publisher was. This way the reader knows it's the material everybody used to call "Stibiconite" but we're not sure what to call it now.

24th Sep 2014 21:08 UTCNorman King 🌟 Expert

Alfredo,

OK, that could be a workable solution. What has to be done? I would guess someone would study the 1862 description, and then look at modern analytical data to see if there is any such data from the type locality, and maybe also what has been accepted as valid stibiconite since then.

This is probably over my head. Nevertheless, where can I find out what the deciding body had to say about stibiconite. Would that be CNMMN of IMA? Is there an index of opinions and/or decisions where I can find that information?

I'm just surprised that, apparently, because there was confusion leading to several things being grouped into stibiconite incorrectly, that would be taken as adequate demonstration that the mineral is invalid. When minerals are found to be different from what they were originally labeled, wouldn't one just determine what that difference is, and establish a new mineral if warranted for the non-conforming material, leaving the old mineral there but with fewer representatives?

In this case, I think I know what to call it: hydroxystibioroméite--if I understood the Atencio et al (2010) paper. :-D

25th Sep 2014 02:18 UTCDaniel Atencio

A complete description of stibiconite is missing in the literature. A complete description should be submitted to CNMNC in order to validate the species.

Regards,

Daniel.

25th Sep 2014 03:04 UTCNorman King 🌟 Expert

Thanks for that information, Daniel.

I visited the IMA site, and this definition appears for “Valid Species (Pre-IMA)--The mineral species is considered valid but was published before 1959, the date the IMA started to approve mineral species. The minerals classified as such (e.g., gold, galena, etc.) would probably rate IMA approval (but not always) if submitted today. All minerals considered valid prior to 1959 were grandfathered as such."

In view of this, especially the last sentence, I am still perplexed by stibiconite having been discredited. Why would we go back and un-grandfather a mineral? In this case, that act left a substance known to exist without a useful label (just look at the trouble we have in referring to what used to be stibiconite!). I do not have a good background here. How often has this happened? What would another example be?

25th Sep 2014 10:03 UTCPeter Haas

It may happen to chrysocolla one day ...

25th Sep 2014 15:21 UTCNorman King 🌟 Expert

Yeah, but then what IS all that stuff? Isn't it nice to have a name?

Chrysocolla is thought to be a mixture--at least some of it is. The stuff that is a mixture therefore would not be a valid mineral. If the remaining material is all amorphous, maybe that would be another problem. But is it all amorphous? (I'll bet we don't know!)

MY stibiconite is precisely Sb⁺³Sb⁺⁵₂O₆(OH). If what YOU have is not Sb⁺³Sb⁺⁵₂O₆(OH), then it is not stibiconite. Where is the difficulty?

25th Sep 2014 17:18 UTCReiner Mielke Expert

Either way I still call my specimens Stibiconite and if the IMA doesn't like it they can sue me. LOL

25th Sep 2014 18:02 UTCDon Saathoff Expert

Reiner, I'm with you!!!

Don

26th Sep 2014 00:58 UTCNorman King 🌟 Expert

Daniel,

I have looked at the Handbook of Mineralogy page, and all the information that is usually provided for any mineral seems to be there for stibiconite. It includes the same information provided for other Lookout Pass isometric minerals I am interested in, avicennite and sénarmontite. Both avicennite and stibiconite include better information than provided for sénarmontite, because the space group information and and X-ray powder pattern for sénarmontite are from synthetic material rather than from the mineral itself, and it is also stated that no modern analysis of the chemistry is available so that information is simply missing for sénarmontite. That substitute information and missing information has not caused a problem for the validity of sénarmontite. Can you tell me what information was missing for stibiconite whose absence was judged to be so important that it was discredited?

26th Sep 2014 01:05 UTCReiner Mielke Expert

I am with you on this Norm, but as you know "You can lead a horse to water but you can't make it drink."

26th Sep 2014 02:00 UTCDoug Daniels

Especially if there's antimony in it....

26th Sep 2014 10:32 UTCDaniel Atencio

Stibiconite is not a discredited mineral. It is a questionable mineral in the IMA list. The stibiconite problem is discussed in http://pubsites.uws.edu.au/ima-cnmnc/MM%2077(1)%20AG%20Christy.pdf.

26th Sep 2014 12:59 UTCNorman King 🌟 Expert

Daniel,

THANK YOU, THANK YOU, THANK YOU!

I knew I could get to the bottom of this if I kept at it. Stibiconite is not discredited, as you said, and the mindat page and other pages that reference stibiconite as invalid are incorrect. This explains why I kept finding very recent (post-2010) papers as well as other websites that mention stibiconite as if nothing had ever happened. As you note, something MAY happen someday, but for now it is “business as usual” for stibiconite as work on the issue of Sb⁺³ continues (page 16 in Christy and Atencio, 2013).

When you are the expert on something, you undoubtedly have it right. But for the rest of us who take in bits and pieces of information about this and that, we often don't have the background or patience to ferret out all of the information and then interpret it correctly. My favorite professor from college (sedimentologist Paul Potter) once told us "When you don't know something, ask someone who does." He was right.

I will discuss this with the mindat managers and see if we can’t get it corrected in mindat until something conclusive is determined for the stibiconite situation.

Again, I appreciate your taking the time to bring me (us) up to speed.

Norman

26th Sep 2014 16:57 UTCRob Woodside 🌟 Manager

Perhaps we should have more choice at Mindat for the IMA drop down status by adding "Questionable" to "No Data", "Discredited", and " Rejected".

edit: Actually "No Data" seems to be the problem.

26th Sep 2014 21:42 UTCNorman King 🌟 Expert

I saw the update for stibiconite on the stibiconite page, and it still isn't right. The first explanatory sentence says "Stibiconite was for a long time an acknowledged species, but is now considered a variety, in line with the revised nomenclature of pyrochlore-supergroup minerals (Atencio et al. 2010)." That sentence is incorrect, and could simply be deleted. The reader should be referred to the two papers co-authored by Atencio. If the reader checks the 2013 paper first, he/she would not become so disoriented.

We already discussed use of the term "variety" in this thread. In the 2010 paper, stibiconite has the same status as the mineral in the roméite group that has Sb³⁺ in the "A" cation position. It is not a variety. BTW, having Sb⁵⁺ in the "B" position is what defines the roméite group. Stibiconite is a full-fledged mineral, analogous to hydroxycalcioroméite, but in the new system of nomenclature it would be hydroxystibioroméite. It is a valid mineral, regardless of its name, even though there are questions at present about how constant the ratio of Sb³⁺ is. Raising that question does not invalidate the mineral, but simply shows where work needs to be done. The correct formula is presumably Sb³⁺Sb⁵⁺₂O₆(OH). It is the extent of variability of Sb³⁺ content, IF ANY, that awaits determination, whereupon we may then re-evaluate the status of stibiconite.

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