Sideronatrite ?

[www.mindat.org] This was sold to me as sideronatrite but I didn't know what the brown mineral was so I sent it and the yellow sideronatrite out for EDS. Now it looks like it might not be sideronatrite because it has a lot of Al in it, I'm thinking it is aluminocopiapite. It is also slightly soluble in water which sideronatrite is not supposed to be. Any ideas on what it is? As for the brown mineral the EDS suggests it might be metavoltine. Any ideas?

Hello Reiner,

sorry but with out a quantification of this spectrum, there is no chance to classify a mineral or even a Sulfate. But Sideronatrite is well known from this location and the mineral looks like the specimen on the picture. The minerals from the Chilean locations are analysis very well by EDS and XRD.

Best wishes
Gunnar

I agree with Gunnar that it looks like sideronatrite, and does not look at all like any copiapite group mineral. Sideronatrite is a bit soluble in water, especially warm water, and it wouldn't be surprising if some Al substituted for part of the Fe³⁺. So I'd go along with the sideronatrite ID.

On a related note, one of my pet peeves is mineral descriptions which include the terms "soluble" and "insoluble". If this is mentioned in a mineral description at all, it should be quantified - How many grams in a litre of water, and at what temperature? Solubility varies so much with temperature, and even with what other minerals and gases are associated in the mix, and particle size is of course enormously important to speed of dissolution. So... classifying minerals as either "soluble" or "insoluble" is like telling the weatherman he is only allowed to describe the temperature using the words "hot" and "cold"



Edited 1 time(s). Last edit at 12/09/2011 11:13AM by Alfredo Petrov.

Ok so the yellow stuff is sideronatrite, what about the brown stuff that it is in? the second pattern is of that and is obviously not the same as the first pattern and obviously not the same mineral.

You will need PXRD analyses for a correct ID.
From my personal experience, copiapite-group minerals often accompany sideronatrite/metasideronatrite, but you can also have natrojarosite (possibly K-/Al-bearing) as an accompanying phase.

Again what about the brown stuff ( second pattern and the stuff the yellow sideronatrite is in)? I think it is metavoltine which is not a copiapite-group mineral. Some people discount the EDS because the mineral looks like something they know and therefore must be, in this case sideronatrite and then others discount both and leave you nowhere. Makes me not want to not do any analysis at all ( like most people) because it never seems to get me any further ahead. So let me turn the tables on this, prove to me it isn't what I say it is. Putting it another way, I have provided some proof why it is what I think it is, what proof have you that it is not what I think it is. If I have to have proof so do you!



Edited 2 time(s). Last edit at 12/09/2011 10:35PM by Reiner Mielke.

I would need the same proof as you: PXRD or SXRD.

I would have to give up mineral collecting if I had to have PXRD or SXRD on ever sample I collected, traded or bought in order to prove what it is. It would be far too expensive. So like most collectors I look at the sort of things mineralogists did before they invented PXRD and SXRD to decide on a name. So unless someone can come up with some proof to the contrary (at the very least EDS) the sample will be labeled Sideronatrite with Metavoltine. Thank you everyone for your input.

Reiner,

It's an intellectually dishonest way of labelling your specimens.

You've been given expert advice that the information you have is insufficient to accurately identify your specimens, yet you choose to ignore this and label your specimen with your chosen name regardless.

It is things like this that pollute our mineralogical knowledge with half-truths and assumptions. Once your specimen is passed onto someone else, who doesn't know the history of your identification, who will know to question it?

The honest way to label it would be to say "Sideronatrite with ?". You could probably justify saying "Sideronatrite with Metavoltine?", but I would go no further than that.

Anyway, for me it's an awful lot of bother for something which is just a fancy kind of rust :)

Jolyon

Reiner, it's great to see you getting some analytical work done, but with SEM/EDAX its hard to get quantitative data, but if you can run some known standards with it, eg some metavoltine or jarosite, you can see if the peak heights match.

Regards,
Ralph

Hello Reiner:

I must say that Jolyon is right in his statement, but I would like also to give my contribution, by the time that I consider myself a reliable amateur and experienced rockhunter of chilean stuff.

Years ago, Dr. Jochen Schluter, has analysd some of So from La Compañia mine, and actually the identified mineral were (all by XRD, some with EDS-SEM)

1) Metasiderontatrite (similar to those arge thick xls embedded in matrix)
2) Metavoltine (flat somewhat prismatic flat shape xls, with 2 main colours: brown and also strong vivid yellow-sulphur like
3) Metalunogen (lemon yellow spots and pustules)
4) Copiapite (light brown to honey brown)
5) Bonattite (azure to sky blue)
6) Rhomboclase (colorless to white)
7) Szomolnokite (yellowish flakes)
8) Butlerite (orange xls)
9) Alumocopiapite (colorless micaceous smooth green colour)
10) Aubertite (light green to somewhat acquamarine like colour)
11) Halotrichite (silky white radial xls)

Then, your sample may be among those....
If is usefull, find attached 2 pics showing typical metavoltine xls from La compañia, hexagonal habit, flat xls of a unconfusionable brown colour


a 3rd pic showing fine grained light brown Copiapite xls masses, and out fo focus, caramel fark brown Jarosite aggregates.
regards
maurizio dini

Thank You Maurizio! You have given me something I can work with unlike some others. Experts with expensive equipment at their disposal will always tell you you need to use the type of equipment they have to properly ID something. Unlike most collectors and dealers, I go to great lengths to make sure of what I have. There is absolutely nothing dishonest about making an informed decision on what you have. If whether or not you had PXRD or SXRD done on your samples is a measure of dishonesty then most mineral collectors would have to be called dishonest. Just sloughing off an inquiry by throwing at someone the disingenuous " you need some expensive analysis done" is not very useful. As it now stands I seem to have some agreement that I have Sideronatrite but since I do not have PXRD or SXRD done on it I guess I don't. I am nowhere with the brown stuff that the "sideronatrite is in. It seems that EDS is totally useless for even taking an educated guess at what it is. I would have been better of taking a fuzzy picture and asking what do you think this is and going with the responses to that.



Edited 1 time(s). Last edit at 12/11/2011 12:59AM by Reiner Mielke.

Let me give you a typical example of what I am often faced with. I recently bought a gold sample with an abundant silver-grey mineral which was labeled Galena and Altaite. I sent it out for EDS and it came back Bi & Te. So now I have the problem of which BiTe mineral is it? A BiTe mineral has never been reported from that mine although at a gold mine not too far away some tellurobismuthite had been found back in the 1940s. Pilsenite has also been reported in the region but is very rare and not confirmed. Based on the color it is likley to be either telluorbismuthite or pilsenite. However it could also be one of the 5 unnamed similar species known. What to do? To get a definitive analysis done would cost thousands of dollars! The dealer I got it from and the person he got it from obviously did not do the analysis and I wouldn't expect them to have done it ( and then sell it to me for $40) but I would not call them dishonest. However I have to give it a name, ? just does not work. So giving it my best guess I am labeling it tellurobismuthite. I would have liked to have been able to call it pilsenite since it is much rarer and more valuable but in all honestly I cannot. Now if someone who buys some or trades some from me gets it analyzed and it turns out to be pilsenite or a new mineral then they got a steal.
Here is the rub, some people on Mindat would say that because I am calling it tellurobismuthite based on inconclusive EDS I am being dishonest, but if I had done nothing and called it galena & altaite, as it was on the labeled it came with, then presumably I would be honest? Calling it tellurobismuthite may or may not be correct but it certainly more correct than galena & altaite. It would seem that not only is ignorance bliss but to some on Mindat it is also honest.



Edited 2 time(s). Last edit at 12/11/2011 01:55PM by Reiner Mielke.

> Unlike most collectors and dealers, I go to great lengths to make sure of what I have.

This is, without question, an admirable quality.

> There is absolutely nothing dishonest about making an informed decision on what you have.

Yes. That's absolutely correct. But then, you came here and asked for advice, and were told quite clearly that the information you had was insufficient to jump to the conclusion that you have. Rather than take that advice, and accept that you may never be able to accurately identify the material on your specimen, you have chosen to ignore it and label it with a name that you think matches.

You are free of course to make whatever decisions about mineral naming that you want to. But if you're just going to ignore advice and go with your gut instinct on what a mineral is, then perhaps you shouldn't be asking us about them.

Jolyon

Hello Jolyon,

There is useful advice and useless advice, but my mistake was telling you what I think, from now on I will keep that to myself.

Hello Alfredo,

"and it wouldn't be surprising if some Al substituted for part of the Fe3+. So I'd go along with the sideronatrite ID."


From the Handbook of Mineralogy:
Chemistry:
(1) (2)
SO3
42.98 43.87
Fe2O3
22.40 21.88
Na2O
17.00 16.98
H2O
17.75 17.27

Total 100.13 100.00

(1) Sierra Gorda [district], Chile; corresponds to Na1.96Fe1.00(SO4)1.92(OH)1.12• 2.96H2O.
(2) Na2Fe(SO4)2(OH)• 3H2O.

Also in Palache et al. 1951, pg 605, of 5 analysis given not a trace of aluminum so why would you expect there to be some? Do you know of any sample of sideronatrite with aluminum in it?

Reiner, I've never looked at any sideronatrite analyses before, and I have no idea whether Al has ever been detected in sideronatrite or not, but what I said was that it would not surprise me if Al were found in sideronatrite. Al-Fe³⁺ quite commonly substitute for each other in many minerals, including sulphates, so why should I be surprised by Al in sideronatrite?

The presence or absence of Al is not definitive for classifying a crystal as sideronatrite, whether or not none has ever been found in it before. Your specimen might turn out not to be sideronatrite. I can't tell that from a photo plus a semi-quantitative analysis. My point was that you cannot say it's not sideronatrite just because it contains aluminium.

Among the many references you could read about Al-Fe³⁺, I'll give just one here: Demartin F, Castellano C, Gramaccioli C M, Campostrini I (2010) Aluminum-for-iron substitution, hydrogen bonding, and a novel structure-type in coquimbite-like minerals, The Canadian Mineralogist, 48, 323-333.

Hello Alfredo,

If sideronatrite with aluminum does not exist then I would say the presence of aluminum is pretty good proof that it is not sideronatrite. Maybe we are looking at a new mineral?
I did find an analysis of sideronatrite from Nova Scotia that contained 1100ppm Al ( and 1200ppm Ca) but such a small amount would never show up in an EDS scan. Someone must have analyzed sideronatrite from there and can tell use if it contains significant Al.

Hello,
I just found (small) amounts of Al studying an "unusual" metasideronatrite. So, surely, Al can substitute Fe3+ also in sideronatrite.

Hello Reiner, I wish mineral ID were simpler than it is, but.... Nature is the way it is. Unfortunately, the statement "If sideronatrite with aluminum does not exist then I would say the presence of aluminum is pretty good proof that it is not sideronatrite." is an example of the "straw man fallacy" in logic. The first part, "If sideronatrite with aluminum does not exist...", is an unproven statement, and the second part "...then I would say the presence of aluminum is pretty good proof that it is not sideronatrite.", is attempting to use the unproven statement to reach a conclusion. Doesn't work. And, as stated before, the presence or absence of subsidiary Al is not part of the species definition.