FMF - Friends of Minerals Forum, discussion and message board

[Cesar M. Salvan]

During the study of the mineralogy ot El Laco magnetite lava flows, we found an interesting mineral: an iron phosphate with cuantitative analysis different to all the described iron phosphates (empirical formula Fe4(PO4)3).

At first, we consider the possibility of a new mineral, but S.E. Haggerty described a mineral with the same composition at El Laco... 38 years ago!. Surprisingly, the mineral remains unnamed and the note of Haggerty is the only published description. Well, is possible that, despite the old citation, the mineral remains "officially" undescribed. But is possible that the mineral is a discredited species or, actually, a valid species with any kind of alteration. I did not found references to clarify these points.
Anybody studied this or similar minerals or could shed light on this issue?

Thanks!

[Jordi Fabre]

John Rakovan ( https://www.users.muohio.edu/rakovajf/ ) kindly assisted us and he sent the message below to be published on his behalf. Thanks John!

With such a request I immediately thought to search the IMA mineral database which was reviewed in Word(s) to the Wise: More than 4000 to be exact, Rocks & Minerals ( https://www.rocksandminerals.org/ ) Vol. 82, p.423-424. This online database allows one to search all IMA approved minerals based on chemistry. The URL is https://rruff.info/ima/ . I did such a search and included Fe, P and O with the exclusion of all other elements. The search resulted in only a few possible minerals. Looking at the composition of these I found no match to the stoichiometry Fe4(PO4)3. Thus, this mineral has yet to be published.

The one potential problem is that if the mineral has been submitted to the IMA and approved as a new mineral, they will not release the name until it has been formally published by the persosn(s) who submitted it. Therefore, it may be IMA accepted but not yet published.

New minerals that are IMA accepted but not yet published are given an IMA number for reference. Such numbers may be available on the searchable website, but I am not certain. I will inquire about this.

I hope that this is of some help.

Sincerely,

John Rakovan - Associate Professor
Mineralogy / Geochemistry
Department of Geology - Miami University
Oxford, OH 45056

[alfredo]

We weren't told how this analysis was made. If it was done by microprobe, which does not detect H, and perhaps overlooked a very minor amount of Na, then this mineral might be IMA 2007-024, which has the same Fe:P ratio.

You can compare with the IMA 2007-024 data on mindat (species # 32197 on mindat). Since this species has already been found at a few localities, even before publication, it might not be so rare.

(If Cesar's formula is in fact the correct one, without water or Na, then of course the mineral would not be IMA 2007-024 and I apologize for wasting readers' time.)

Regards,
Alfredo

[Cesar M. Salvan]

Thanks for the response.
I just need to know if anybody studied the locality or recognize the mineral. I do not want to waste time in the analytical protocol for new species if the mineral has been described or under study.
Of course, my first action was a search in the IMA database. If the mineral was actually identified in 1970, is quite odd that the mineral has not been further studied...but appears to be undescribed.

In response to the guess of Alfredo, the crystals are free of Na and FTIR spectrometry shows lack of OH and H2O.

Thanks again for the responses. I hope to update this topic in the future with all the data.

Cesar

[alfredo]

Cesar, I think it's not so strange that nothing further was published on your mineral after 1970, because many species are never described sufficiently for submission to the IMA. Likely it was never submitted to the IMA, so it has no IMA number or proposed name.

If it has no OH or water, then the formula would have to be something like
Fe(II)3 Fe(III) (PO4)3 to maintain charge balance, or have I missed other possibilities?

Anyway, I congratulate you on your find and hope you have a new species.

Alfredo

[Cesar M. Salvan]

Alfredo,

Thanks! I hope too that we have a new species!
Now, we are performing the pertinent analytical study and I think that we will prepare a proposal to IMA.

I think you are right with the formula. We are confirming that using XPS.

Well, thanks again for the support to you, John Rakovan and, especially, to Jordi, for his continuous efforts.

Cesar

[Jordi Fabre]

And also to Marie Huizing from Rock & Minerals: https://www.rocksandminerals.org/ for her great help connecting people.

Jordi

[lluis]

Good afternoon.

Congratulations to Cesar.

But I am still intrigued.
I saw same as Alfredo, that should be with this formula a Fe(II)3Fe(III)(PO4)3.

But as far as I know, when there is Fe3+ and Fe2+, products usually have a very dark color. And it is the color one could expect for a Fe3+
Also, Fe3+ is a faint violet if not hydroxy ions near (or any convenient complexant, I mean...)

Really puzzled...
I think to see that the sprays are over magnetite...
Could not be that it was a partial pseudo of vivianite to santabarbaraite?
And for that the two oxidation states of Fe?

I know that you found not hydroxil, but then, why this color?
Really puzzled

Well, life is learning...
May you be so kind to post further developements in this specimen analysis?

With best wishes

Lluís

[Cesar M. Salvan]

Thanks, Lluis, for the congratulations, but is very soon I think.

First, we are determining unambiguously if actually we have a new species, then we will confirm the actual formula and if all is ok and IMA finally accept the species, publish the data. Until the completion of the lab work and conclusions obtaining, I prefer not to comment the results or discuss other aspects or properties of the material.

Of course, If the analysis shows that we have an alteration, solid solution or mixture of described phases, I will comment it here for completion of the topic.