Fluor-cannilloite - Luc Yen, Yenbai Province, Vietnam

Is this not pargasite?

Hello, Peter!

Well, this is a can of worms, for sure. The specimen is from the Donald F. Phillips collection–certainly a credible source (via Dakota Matrix Minerals). I will look into whether there is any information about an analysis.

This information was supplied by Uwe Kolitsch in response to a previous discussion about pargasite vs. fluor-connilloite at Luc Yen:

“Correspondence [with previous uploader] showed that specimen was not analysed and could in fact be fluor-cannilloite (uploader told me that according to amphibole specialist Prof. Frank Hawthorne all these xls are fluor-cannilloite - they are, however, usually sold as paragasite [sic] in recent years).” [from--[www.mindat.org]]

That response suggests that it is fluor-cannolloite and not pargasite.

However, in that thread Phillipe Russo then said he thinks the analyses are coming back pargasite. But we don't really know what has been analyzed, compared to the specimen I have (see below).

Also, note this discussion on the Luc Yen locality page:

'NOTE: Some of the "pargasites" from here may be fluor-cannilloites, and vice-versa (see [www.mindat.org] and [www.mindat.org]). Hauzenberger et al. (2005) report intense green pargasite in association with red spinel from Luc Yen. This pargasite has been confirmed by EPMA and single-crystal XRD.'

I interpret my specimen not to be intense green. I actually increased the contrast a bit because the original photos were rather washed out. Specimens on the pargasite page from this locality are not quite like in the photo I uploaded. They seem darker and the crystals are much coarser.

I believe I can get an analysis done, if it comes to that. Aren’t amphiboles fun?

Norman,

I have not been able to find any analytical data supporting the ocurance of fluor-cannilloite from Luc-Yen. Although Hawthorne et al (1996) suggests that fluoro-cannilloite probably occurs at several locations, it appears that the up to 0.15 x 0.15 x 0.20mm grains from Pargas are the only confirmed occurance so far. The type description of fluor-cannilliote is available as a free download both at minsocam and rruff.

Although pargasite seems to be the dominant (and only published) amphibole at Luc Yen, I would expect that several Ca, Mg and Al-rich amphibole species occur in the corundum and spinel bearing marbles, as is the case from the geologically similar Mogok occurances where several edenite, pargasite, sanadagaite species are identified.

I have sent an e-mail to Prof. Hawthorne asking him if he is aware of any confirmed fluor-cannilloite from Luc Yen.

Olav

In all this, we are still not talking about my sample, and possibly not about other samples that resemble mine (I may be mistaken about the latter point, yet it does seem that the posted photos of pargasite from Luc Yen show a darker green and coarser material). I would be glad to send my sample to someone who can analyze it and properly interpret the data.

Based on comments in Hawthorne, et al. (1996, see especially the last sentence before "Acknowledgments" on p. 1002), it could be present at Luc Yen. Now I am curious about the information provided by the poster referred to by Uwe Kolitsch, citing comments by Hawthorne. Of course, we are always learning new things, and the state of knowledge changes.

I took the sample of questionable fluor-cannilloite outside for natural light and took these photos of different sides. Here you can better appreciate the light coloration and fine texture. The penny is 19 mm in diameter.

Norman,

You are absolutely right in that your specimen may well be fluor-cannilloite.

My comments can basicly be summarized in the three following statements

1) I have not been able to find any hard evidence ( ie- published analytical data) that fluor-cannilloite has been found at Luc Yen.
2) It is documented that other more common amphiboles (read pargasite) is relatively abundant.
3) The similarity with the geological environment in Mogok, supports the idea that multiple specimens of Ca,Mg,Al-rich amphiboles should be present. At Luc Yen, fluor-canniloite can be one of them, although not (to my limited knowledge) yet identified.

An analysis of your specimen will certainly be most interesting, and even more so if it can be confirmed that fluor-cannilloite has been identified from Luc Yen before.

Olav

I analyzed in past several (about 4-5) samples labelled "fluor-cannilloite" (at first, from "Yuang Yang", then from Luc Yen) coming from different sources and all of them were very convincing pargasites. Ca content was definitely too low and Na, instead, was as it should be in pargasites. Some of my colleagues (Dr.Nikita Chukanov, for ex.) also analyzed similar material with same result. So, to my knowledge too, there is no evidence of existence of fluor-cannilloite in Luc Yen. I would say this mineral is extremely rare, I was able to find it only in polished section on material from Pargas. And, honestly, I doubt much that Frank Hawthorne could ever say that "all these xls are fluor-cannilloite"

Norman,

The reply from Frank Hawthorn on my inquiry was as follows:

"No, I am not aware of any such evidence. I have analyzed the amphibole from the Luc Yen locality.......it is pargasite.

It looks nothing like fluor-cannilloite (from Pargas, Finland) which occurs as very small insignificant crystals. Note that large crystals of brownish pargasite also occur at Pargas."

best regards

Olav

Olav and others,

Thank you for getting to the bottom of this. I changed the photo information for my specimen and the photo description on mindat.

The locality page for Luc Yen, Yenbai Province, Vietnam still shows fluor-cannilloite as occurring there, but it seems that Frank Hawthorne's comment definitively shows that to be incorrect. Should it be deleted from the mineral list? Does anyone know why it was added in the first place? (The last question is somewhat rhetorical!)

I was impressed by the more delicate form and coloration of my material than what is shown in other photos of pargasite posted for that locality. Other mineral occurrences coming to mind where rock bodies vary from place to place, and I still wonder if every green amphibole from there will turn out to be pargasite. But it seems that fluor-cannilloite shouldn't be in the mineral list for Luc Yen based on speculation that it MIGHT occur there.



Edited 2 time(s). Last edit at 05/05/2012 01:39PM by Norman King.

Thanks all. Fixed locality page.