Discussions

💬 Home 🔎 Search 📅 Latest

╳Discussions

💬 Home 🔎 Search 📅 Latest

Groups

Recent Images in Discussions

Improving Mindat.orgMatiollite from Corrego Pomaroli mine

8th Apr 2010 20:38 UTCKnut Eldjarn 🌟 Manager

The specimen first used as head-photo of "Burangaite" and now used for the Burangaite-Matioliite-series was obtained by me from Excalibur minerals (ref. Tony Nikitscher). An EDS was performed on the crystals by H. Folvik at the Oslo Mineralogical Museum showing a clearly Mg-dominant Matoliite - as could be expected from the ligh colour. Matoliite should therefore be listed for the Corrego Pomaroli mine and "Burangaite" either kept with a question mark or deleted. According to Tony Nikitscher no chemical analysis has been performed previously on the material he obtained and I have seen no chemical data published. The photo should probably be moved as the head photo for Matioliite since the best crystals of the mineral probably come from this locality.

Knut

11th Apr 2010 00:26 UTCLuiz Alberto Dias Menezes, Fo.

Knut:

I was who sold "burangaite" specimens to Tony Nikisher, based on a X-ray analysis (I could not conduct chemical analysis at that time because the micro=probe I was allowed to use was broken); at the same Tucson show when Tony bought them from me I sold one specimen to Jim Nizamoff, another to Skip Simmons and a third to Al Falster, and they soon informed me that they found a higher Mg than Fe content so it would be a new mineral; they started to describe it but Paulo Matioli (that was subject of a discussion in Mindat 2 years ago under the title "An Unescrupulous Mineral Swaper", due to the several trading scams he was involved in) and Daniel Atencio were already working on this material, on a more advanced stage, and they soon submitted it to IMA and have it approved as matioliite.

The only locality I know for this material is the type one: Gentil mine, Mendes Pimentel; I have not heard of "Corrego Pomaroli"; Fazenda Pomaroli (=Pomaroli farm) is a large land property inside the Linópolis district where several pegmatites are located, but it is labout 3 km away from the border of Mendes Pimentel county, where Gentil mine is located. When I sold the specimens to Tony/Jim/Skip/Al/Renato Pagano I labelled them as from Linópolis, because it was what my supplier had told me they had came from; when I saw the publication of matioliite and found out that it was from Gentil mine I questioned my supplier and he admitted it was from there.

Please ask Tony if the specimen he sold you was bought from me.

Regards

Luiz

12th Apr 2010 21:09 UTCKnut Eldjarn 🌟 Manager

Luiz,

I have corresponded with Tony Nikitscher, but he does not remember if the "Burangaite" specimens came from you or Carlos Barbosa. The only locality information I have comes from Tony`s label.Since Carlos was winding down his business at the time, I suspect you were the source. If you now know there is only ONE locality for this mineral (type locality for Matioliite) in Brazil, the information in Mindat should be changed.

Best regards:

Knut

12th Apr 2010 22:02 UTCJeff Weissman Expert

Based on my record entry number of 8211, I estimate that I first photographed a specimen from Excalibur in 2004 - my guess is that the material was obtained at this time and offered for sale, labeled as being from "Linopolis", so I am guessing that Luiz is indeed the source of these specimens. I will change my label to 'matioliite' and change the locality accordingly.

See http://www.mindat.org/photo-138006.html

Thanks for the discussion and resolution!

Jeff

12th Apr 2010 22:13 UTCKnut Edvard Larsen 🌟 Manager

Thanks for the information.

Atencio et al (2006) http://rruff.info/rruff_1.0/uploads/AM91_1932.pdf, says:

"Bermanec et al. (2004a,2004b) described "burangaite" as bluish long prismatic crystals, intimately associated with brazilianite, at the Córrego Pomarolli area, Linópolis, Divino das Laranjeiras, Minas Gerais, Brazil. Chemical data, however, show that Mg predominates over Fe.

The mineral ......is probably matioliite ".

I also notice that they say about matioliite from the Gentil mine : "Some crystals (are zoned to more Fe-rich compositions with an Fe2+:Mg ratio of approximately 1:1, corresponding to an intermediate member of the burangaite-matioliite solid-solution series".

If then Gentil mine = Córrego Pomarolli area, both matioliite and burangaite-matioliite series does exist at the locality.

12th Apr 2010 23:13 UTCKnut Eldjarn 🌟 Manager

Knut Edvard,

I know the publication, but according to Luiz the alleged locality seems to be the same as the type locality for Matioliite and these should be merged. Taking the uncertainty of measurement into account their analytical data DOES NOT confirm the presence of Burangaite at the locality and the Mindat info should be changed accordingly. If you want to distinguish between "Matioliite" and "Burangaite-Matioliite series" - in reality ONLY the latter has been described from Brazil since the type material of Matioliite is not a pure end-member but includes a substantial amount of iron in the structure... This just illustrates an unnecessary accumulation of data in Mindat. A number of minerals represent such series where nearly all samples assigned an end-member name will in reality be a member of the series.. In my view a listing of i.e. "Burangaite-Matioliite-series" and similar series in Mindat should have a reference to the respective end-members for localities - AND a listing ONLY of localities where data is lacking concerning which end-member may be present. This listing could me mended as data becomes available and one or more correct end-member names is assigned to the material from a given locality.

Knut

14th Apr 2010 19:38 UTCUwe Kolitsch Manager

Burangaite-Matioliite Series or other ... Series should be used when

a) no chemical-analytical data are available, but it's clear from other methods (XRD, spectroscopy, ...) that one deals with this specific series (this applies to a lot of specimens in collections and on the market)

b) when semiquantitative or quantitative chemical-analytical data are available which point to a 1:1 intermediate composition where it's impossible to judge from the analyses if one or the other or both end-members are present.

"... unnecessary accumulation of data in Mindat"

Clearly not true.

14th Apr 2010 20:25 UTCKnut Edvard Larsen 🌟 Manager

Commentary added on the Gentil Claim page.

The burangaite-matioliite series entry at the Córrego Pomarolli page http://www.mindat.org/loc.php?loc=7719&ob=4: is removed according to the info above.

The references given for the remaining minerals listed is MinRec 14:234. Looking this up i discovered that this is a reference not to to Córrego Pomarolli but to Pamaró mine (Also called Pamaroli mine , Pamarol or Morro do Cruzeiro). This is according to the reference located

3 km NW of João Modesto Mine http://www.mindat.org/loc-7717.html. and North of Linopolis

For me it seems that Córrego Pomarolli mine- is an erronous non-existing mine, but that somebody has confused Pomarolli with Pamaroli.

So no need to merge it with the Gentil mine, just doing some clean-up.

Luiz: Would Pamaró MIne (Pamaroli; Morro do Cruzeiro; Pamarol) ,Linópolis, Divino das Laranjeiras, Doce valley, Minas Gerais, Southeast Region, Brazil be the correct hierachi for that locality?

14th Apr 2010 23:08 UTCKnut Eldjarn 🌟 Manager

Uwe,

I agree with you - except for the way your b) has been interpreted for some series and localities. There are i.e. localities that list both "Grossular", "Andradite" and "Andradite-Grossular-series". To do it correctly a huge number of additional localities with analysis showing the presence of both members of a series - and different intermediates should be listed in this way creating an unnecessary accumulation of data. I still think that is a waste. It would be better to list under i.e. "Andradite-Grossular-series" only those localities were garnets belonging to this group have been identified but without data clearly assigning them to one or the other mineral. In this way localities listed under the -series will indicate a need for chemical data to be able to assign the minerals to one - or both end-members of the group.

Knut

17th Apr 2010 22:55 UTCUwe Kolitsch Manager

> There are i.e. localities that list both "Grossular", "Andradite" and "Andradite-Grossular-series".

I agree it's redundant, but some literature reference may give "Andradite-Grossular-series" and another one "Grossular" or "Andradite". We shouldn't just delete the reference for the series, because someone might want to look it up for further reading. It may also indicate that intermediate members are common at this locality.

Photo uploaders should choose "Andradite-Grossular-series" whenever they have no confirmation for one of the end members.

18th Apr 2010 02:47 UTCPeter Haas

Too complicate things even further, the indivdual references may be based on a different number of analyses or provide different information about the analyses that were carried out. If, for example, one reference states that more than 100 specimens were investigated and that they were all andradites (backed up by the full set of data and a complete method description), and another one states that grossular was confirmed in one sample (with incomplete analytical data), it is likely that the second reference is not reliable. But it's only that: likely, NOT safe. Thus, even in this case, there is a good reason to keep both references.

Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2024, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: April 25, 2024 05:46:23

Go to top of page