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Improving Mindat.orgDoes "true" lipscombite really occur in nature?
1st Dec 2019 18:14 UTCDan Polhemus
Following up on the Variety Names for Photos thread, the following is presented for comment:
The phosphate mineral lipscombite was characterized based on artificially synthesized material with a formula of Fe2+Fe3+2(PO4)2(OH)2 (Katz & Lipscomb 1951)
It was first reported under natural conditions from the Sapucaia Mine in Brazil by Lindberg (1962), but in a manganoan form with the formula (Fe2+Mn2+)Fe3+2(PO4)2(OH)2.
The species zinclipscombite was subsequently described by Chukanov et al. (2007) from Silver Coin Mine in Nevada, with the formula ZnFe3+2(PO4)2(OH)2.
Adams et al. (2015) analyzed multiple specimens from the Silver Coin Mine and stated that “the majority of the black to very dark green lipscombite from the Phosphate Stope and Arsenate Drift could be considered zinclipscombite since zinc constitutes greater than 16% of the combination of divalent and trivalent cations.” However these authors also note that “Of the several dozen lipscombites examined in this study, those with medium brown to paler brown-green color still often contained some zinc, but not in sufficient quantity to be considered zinclipscombite” and conclude that “identification of a particular sample as zinclipscombite can be problematic”.
It is not clear that any peer-reviewed study to date has actually documented lipscombite with a composition of Fe2+Fe3+2 (PO4)2(OH)2 in a natural (versus artificially synthesized) setting, although the Adams et al. (2005) study implies that it might exist at the Silver Coin.
The lipscombite page on Mindat indicates the type-locality of lipscombite as the Sapucaia Mine in Brazil, even though this locality contains a manganese-rich variant that does not match the original formula given by (Katz & Lipscomb 1951).
Does it really make sense for Mindat to list a mineral and formula that has never been shown to occur under natural conditions? At the very least, the work of Adams et al. (2015) would suggest that there is a continuously varying solid solution series from low-zinc to high-zinc lipscombite at the Silver Coin Mine, but not necessarily any unequivocally zinc-free lipscombite. Similarly, the Brazilian material analyzed by Lindberg (1962) that forms the basis for the type-locality listed on Mindat contained significant amounts of manganese.
These confounding aspects of composition, and absence of proper characterization in nature, caused Huminicki & Hawthorne (2002) to consider lipscombite as "an enigma" in their comprehensive review paper on the crystal chemistry of phosphate minerals. At the very least, it might be advisable to edit the lipscombite page on Mindat to reflect these findings, and to note that the optimal formula is based on artificially synthesized material that has never been conclusively validated outside a laboratory.
References:
Adams, P. M., W. S. Wise and A. R. Kampf. 2015. The Silver Coin Mine, Iron Point District, Humboldt County, Nevada. The Mineralogical Record 46: 701–728.
Chukanov, N. V., I. V. Pekov, S. M. Ckel, A. E. Zadov & V. T. Dubinchuk. 2006. Zinclipscombite ZnFe3+2(PO4)2(OH)2—a new mineral. Proceedings of the Russian
Mineralogical Society, 135: 13–18.
Huminicki, D. M. C. and F. C. Hawthorne. 2002. The crystal chemistry of the phosphate minerals. Reviews in Mineralogy and Geochemistry 48: 123–253.
Katz, L. & W. N. Lipscomb. 1951. The crystal structure of iron lazulite, a synthetic mineral related to lazulite. Acta Crystallographica 4: 345-348.
Lindberg, M. L. 1962. Manganoan lipscombite from the Sapucaia Pegamatite Mine, Minas Gerais, Brazil, first occurrence of lipscombite in nature. The American Mineralogist 47: 353–359.
The phosphate mineral lipscombite was characterized based on artificially synthesized material with a formula of Fe2+Fe3+2(PO4)2(OH)2 (Katz & Lipscomb 1951)
It was first reported under natural conditions from the Sapucaia Mine in Brazil by Lindberg (1962), but in a manganoan form with the formula (Fe2+Mn2+)Fe3+2(PO4)2(OH)2.
The species zinclipscombite was subsequently described by Chukanov et al. (2007) from Silver Coin Mine in Nevada, with the formula ZnFe3+2(PO4)2(OH)2.
Adams et al. (2015) analyzed multiple specimens from the Silver Coin Mine and stated that “the majority of the black to very dark green lipscombite from the Phosphate Stope and Arsenate Drift could be considered zinclipscombite since zinc constitutes greater than 16% of the combination of divalent and trivalent cations.” However these authors also note that “Of the several dozen lipscombites examined in this study, those with medium brown to paler brown-green color still often contained some zinc, but not in sufficient quantity to be considered zinclipscombite” and conclude that “identification of a particular sample as zinclipscombite can be problematic”.
It is not clear that any peer-reviewed study to date has actually documented lipscombite with a composition of Fe2+Fe3+2 (PO4)2(OH)2 in a natural (versus artificially synthesized) setting, although the Adams et al. (2005) study implies that it might exist at the Silver Coin.
The lipscombite page on Mindat indicates the type-locality of lipscombite as the Sapucaia Mine in Brazil, even though this locality contains a manganese-rich variant that does not match the original formula given by (Katz & Lipscomb 1951).
Does it really make sense for Mindat to list a mineral and formula that has never been shown to occur under natural conditions? At the very least, the work of Adams et al. (2015) would suggest that there is a continuously varying solid solution series from low-zinc to high-zinc lipscombite at the Silver Coin Mine, but not necessarily any unequivocally zinc-free lipscombite. Similarly, the Brazilian material analyzed by Lindberg (1962) that forms the basis for the type-locality listed on Mindat contained significant amounts of manganese.
These confounding aspects of composition, and absence of proper characterization in nature, caused Huminicki & Hawthorne (2002) to consider lipscombite as "an enigma" in their comprehensive review paper on the crystal chemistry of phosphate minerals. At the very least, it might be advisable to edit the lipscombite page on Mindat to reflect these findings, and to note that the optimal formula is based on artificially synthesized material that has never been conclusively validated outside a laboratory.
References:
Adams, P. M., W. S. Wise and A. R. Kampf. 2015. The Silver Coin Mine, Iron Point District, Humboldt County, Nevada. The Mineralogical Record 46: 701–728.
Chukanov, N. V., I. V. Pekov, S. M. Ckel, A. E. Zadov & V. T. Dubinchuk. 2006. Zinclipscombite ZnFe3+2(PO4)2(OH)2—a new mineral. Proceedings of the Russian
Mineralogical Society, 135: 13–18.
Huminicki, D. M. C. and F. C. Hawthorne. 2002. The crystal chemistry of the phosphate minerals. Reviews in Mineralogy and Geochemistry 48: 123–253.
Katz, L. & W. N. Lipscomb. 1951. The crystal structure of iron lazulite, a synthetic mineral related to lazulite. Acta Crystallographica 4: 345-348.
Lindberg, M. L. 1962. Manganoan lipscombite from the Sapucaia Pegamatite Mine, Minas Gerais, Brazil, first occurrence of lipscombite in nature. The American Mineralogist 47: 353–359.
1st Dec 2019 19:12 UTCUwe Kolitsch Manager
Vencato, I., Mattievich, E. and Mascarenhas, Y. P. (1989): Crystal structure of synthetic lipscombite: a redetermination. Am. Mineral. 74, 456-460.
Matvienko, E. N.; Yakubovich, O. V.; Simonov, M. A.; Belov, N. V. (1981): Crystal structure of synthetic lipscombite (Fe73+(Fe0.53+Fe0.52+)18[PO4]14(OH)24) with partial ordering of iron(III). Zh. Strukt. Khim. 22, 121-125 (in Russian).
Rouzies, D.; Moral, P.; Millet, J. M. M. (1995): Synthesis and Study by Moessbauer Spectroscopy of Lipscombite (Fe3+2Fe2+(PO4)2(OH)2) Partially Substituted by Manganese, Cobalt, and Chromium Cations. J. Phys. Chem. 99(33), 12576-12580.
The latter two are currently missing on the Mindat page - will add them.
EDIT: More:
Rouzies, Dominique; Varloud, Jean; Millet, Jean-Marc M. M. (1994): Thermal behavior and physico-chemical characterization of synthetic and natural iron hydroxyphosphates. J. Chem. Soc., Faraday Trans. 90(21), 3335-3339.
Yanning Song, Peter Y. Zavalij, Natasha A. Chernova, and M. Stanley Whittingham (2005): Synthesis, Crystal Structure, and Electrochemical and Magnetic Study of New Iron (III) Hydroxyl-Phosphates, Isostructural with Lipscombite. Chem. Mater. 17, 1139-1147.
1st Dec 2019 19:16 UTCAlfredo Petrov Manager
In the absence of a formal discreditation proposal to the IMA, the only thing we can do is make note of the doubts on the lipscombite page, or add a link to this discussion.
1st Dec 2019 19:53 UTCFrank K. Mazdab 🌟 Manager
I'd presume if the (Fe2+, Mn2+, Zn, Mg, etc.) site is a single site, and even in the Mn-rich material if Fe2+ is still greater than Mn2+, and also still greater than any lesser M2+ components in the site, and if none of those lesser components are required to stabilize the composition (which the artificial material suggests is not the case), then the end-member composition would still be considered to be Fe2+Fe3+2(PO4)2(OH)2, even if natural material of that purity has not yet been found.
It reminds me a bit of axinite-(Mg) ("magnesio-axinite"). Although an essentially end-member single cut gemstone from somewhere in East Africa had been known since the early 1970s, for a long time, axinite-(Mg), for all practical purposes, was really a messy solid solution between it and the Fe- and Mn-end-members, where the Mg barely exceeded the Fe and Mn (the Ludwig skarn in NV, was a well-known locality for these barely-Mg axinite-(Mg) samples). It strikes me that the all-Fe synthetic lipscombite in a way is not so different from the original unknown-locality faceted axinite-Mg. Later, that unknown locality for axinite-(Mg) was found to be Merelani, and likely in the right environment, that all-Fe lipscombite will eventually be discovered too.
1st Dec 2019 20:16 UTCRalph S Bottrill 🌟 Manager
It sounds highly likely that Fe2+ dominant lipscombite will exist naturally, just needs someone to do the analyses. As to whether we can talk about Zn-free lipscombite will depend on how precise your analyses are.
A part of this problem is whether we should show mineral formulae as hypothetical end members or more empirical versions showing the typical range of compositions. Eg. if you look at micas, many, eg annite, show a hypothetical end member composition, which may not exist in nature, while others, eg wonesite, show complex substitutions in nearly every site, though they probably both have similar degrees of variable composition. This must be incredibly confusing for novices. Probably we need two formulae for most minerals, one showing a hypothetical end member, one showing the major possible substitutions. But again, what constitutes significance in elemental substitution: 10%, 1%...?
1st Dec 2019 20:59 UTCFrank K. Mazdab 🌟 Manager
definitely agree with you about showing end-member formulas here, because we'll quickly discover that some minerals don't have balance-able end-member formulas, typically because there are often multiple exchange vectors whose outcomes have all been lumped into one formula, and no one has bothered working out if each of these should define an end-member. I think a lot can be learned from uncovering these "un-balance-able" species.
I also like the idea of showing, in addition to an end-member formula (if one exists), an additional "working" formula that includes the major substitutions one is likely to find, for example, while doing microprobe work. Since for example the quality of much microprobe data is judged whether it falls within the 99%-101% analytical total range (accounting for calculated components like H2O), perhaps the common occurrence of a substitution at ~1% might be a good (albeit arbitrary) cutoff criteria for us to include as notable substituting elements in such a working formula?
So lipscombite proper might get a its end-member formula of Fe2+Fe3+2(PO4)2(OH)2 but its "working" formula of (Fe2+,Mn2+,Zn)Fe3+2(PO4)2(OH)2?
2nd Dec 2019 04:19 UTCDan Polhemus
I like your suggestion of providing the hypothetical end-member formula (even if it has never be definitively demonstrated to occur outside a laboratory setting) along with a "working" formula that reflects the reality of what we have actually observed in naturally occurring specimens properly analyzed to date.
So for lipscombite, perhaps the "working" formula could be more along the lines of
(Fe2+,A)Fe3+2(PO4)2(OH)2 where A = Mn2+ or Zn, since at a minimum some amount of Fe2+ would need to be present for it to be lipscombite in any sense of the original description?
2nd Dec 2019 05:00 UTCFrank K. Mazdab 🌟 Manager
(Fe2+,Mn2+,Zn)Fe3+2(PO4)2(OH)2 already does indicate that Fe2+ is the dominant cation in the M2+ site, because it is listed first among the cations in that site. After that, whether Mn2+ or Zn should be listed second I suppose depends on whether Mn2+-enriched varieties or Zn-enriched varieties are more widespread or more well-known, although in some regards, it really doesn't matter much because it's just an academic concern, since the critical Fe2+ is already emphasized as the first element. Presumably zinclipscombite would be (Zn, Fe2+,Mn2+)Fe3+2(PO4)2(OH)2, where Zn>Fe2+ and Zn>Mn2+ (but note that Zn need not be greater than ∑[Fe2++Mn2+], assuming of course that the divalent cations are preferentially distributed into one particular site).
2nd Dec 2019 06:06 UTCOlav Revheim Manager
Dan Polhemus ✉️
It was first reported under natural conditions from the Sapucaia Mine in Brazil by Lindberg (1962), but in a manganoan form with the formula (Fe2+Mn2+)Fe3+2(PO4)2(OH)2.By reading the paper, it becomes obvious that the specimen analysed by Lindberg actually is Mn dominant (Mn2+Fe2+)Fe3+2(PO4)2(OH)2, see table 1 in here:
So Dan's question is actually valid, unless some of the references Uwe provided shows otherwise. Either way, the occurance in Sapucaia Mine should probably be labelled as questionable or erroneous
Olav
Olav
2nd Dec 2019 06:36 UTCFrank K. Mazdab 🌟 Manager
Also of note is that mindat lists some 52 localities for lipscombite, so before we get too trigger-happy and unilaterally "discredit" the mineral ourseleves, we probably really ought to sift through those localities, see which of them include references that themselves include high-quality analytical data, and check if any Fe2+>Mn2+ examples actually do exist.
(as an aside, I love being able to freely use superscripts and subscripts now!!! :-) )
9th Dec 2019 02:26 UTCDan Polhemus
So after all this discussion, where does this leave us in regard to lipscombite?
We have zinclipscombite, described by Chukanov et al. 2007, who stated that its formula contains no Fe2+. Presumably a certain limited amount of Fe2+ could be present and we would still consider the sample to represent this species, within the bounds of how we handle cationic substitution in continuously varying series. But overall this is the zinc-rich end member, and is a separately recognized species that is not lipscombite per se.
We also have a manganese-rich variety characterized by Lindberg (1962) from Sapucaia, Brazil. His data, however, indicate that the ratio of Mn2+ to Fe2+ is greater than 2:1, which, if we follow the same standard used to define zinclipscombite as a separate species would also indicate that his material should be considered something different from lipsocombite as well, presumably "manganolipscombite" if anyone cared to petition the IMA. Although Sapucaia is given as the type-locality for lipscombite in nature, this seems wrong, since the material occurring here is apparently not really lipscombite in the sense of having a predominance of Fe2+.
As such, the type-locality for lipscombite as currently recognized appears to be someone's laboratory.
Several photos posted on Mindat from the Silver Coin Mine in Nevada (DXV-JMC), the Clara Mine in Germany (RRR-1D8, H4T-NNG, K0H-218), and Minas Gerais, Brazil (RT6-EWY, M8D-KJD) show examples of putative lipscombite that are indicated to have been analyzed, and as such might in fact validate the existence of Fe2+-dominant "true" lipscombite in the field. If so, then it would seem that one of these localities could serve as a proper type-locality. However, these captions provide no indication of cation composition. It is also not stated as to what these analyses consisted of, or what they might actually tell us (composition, crystal structure, etc.), nor have these data been externally reviewed.
So for now, it seems that there is no peer-reviewed study that actually validates the presence of true lipscombite in nature.
Suggest that the lipscombite page be edited accordingly.
9th Dec 2019 03:25 UTCFrank K. Mazdab 🌟 Manager
certainly a note can be added to the lipscombite page that the type locality material appears to be Mn2+>Fe2+ (but based on a pre-microprobe analysis that even its authors remark might be a bit "iffy" with regards to an accurate Fe3+/∑Fe ratio), that the literature describing lipscombite from other localities have not been evaluated here (yet) for any analytical data that might indicate their Mn2+/Fe2+ ratios, and the possibility exists that the Fe2+-dominant composition for which the mineral is officially defined may only be known from synthetic material.
Beyond such a note, I'm loathe (and suspect others here would be too) to ostensibly unilaterally "discredit" lipscombite here on mindat, when the IMA still seems OK with its existence (not that the IMA is necessarily always on the ball with such matters).
If this works in the short-term, I could certainly do that. In the longer term, if you feel particularly motivated and have the time, you might wish to explore this further by going through the lipscombite locality list, looking up the references for each locality (there seem to be ~50), and seeing if any of the listed references include high-quality analyses. It may be faster for enthusiastic members here with interests in particular species to accomplish these sorts of tasks, rather than to necessarily wait for the tasks to ascend to the top of managers' queues... :-)
EDIT: OK, I added what I wrote above (~paragraph 1) as a formula note on the lipscombite page.
9th Dec 2019 04:23 UTCDan Polhemus
What you suggest sounds fine.
I am not looking to discredit lipscombite, which probably does exist, somewhere, in its optimal formula or something close to it. And Mindat would not be the place do to that anyway.
I am just trying to clean up the page for this particular mineral to make it more reflective of the scientific reality as currently documented. With luck, someone will eventually publish a peer-reviewed study showing that true lipscombite actually exists outside of the laboratory.
And as noted in the preceding discussion this thread, this problem exists for other minerals as well in terms of hypothetical end member states, so there are broader implications to the conversation.
31st Jul 2020 05:50 UTCHerwig Pelckmans
* Has any "true" lipscombite (= more Fe than Mn) been found in nature?
If not, the next obvious question is: what are all those lipscombite specimens mentioned under lipscombite?
Cheers, Herwig
ACAM & MKA (Belgium)
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