Magnesiohornblende, Eifel Germany

According to the information on the locality page Nickenicher Sattel (Eicher Sattel), the photos:

© Chinellato Matteo

.

© Chinellato Matteo

in the magnesiohornblende should probably be moved to the amphibole group gallery.

Same probably goes with:



also labeled magnesiohornblende, but from Monte Somma/Vesuvius in Italy

Olav



Edited 3 time(s). Last edit at 11/30/2010 08:11PM by Rock Currier.

“magnesiohornblende should probably be moved to the amphibole group gallery”
We can do that. For me it is/was more interesting to show, how the “misidentified magnesiohornblende looks like.
Christof

Christof - I have no opinion one way or the other, lets get it right! Unfortunately, almost all of the references listed for the locality are all in German?, which I can't read or access, so I can't check to see if there are any published analysis which could provide a clue. Since you are the only editor of this mineral entry, what was your basis for the "erroneously and without analytical data named Magnesiohornblende" statement - have you analyzed any of these. I photographed the specimen from a reliable source who takes great care in accurate identifications, although mistakes and errors do arise.

Also, there are some identical appearing images of orange prismatic crystals under 'kaersutite' - [www.mindat.org] - one of these has been confirmed , could these "magnesiohornblendes" all be kaersutite? or what is the difference?

thanks

Jeff,
with less exceptions (Obertiite, rock-forming amphiboles in mantle xenoliths) one cannot find any information about the composition of amphiboles from the Eifel area.
The naming convention, to call the black amphiboles from the Eifel "Ferrohornblende" and the orange-red ones "Magnesiohornblende", has developed between mineral collectors because they "want" individual names for minerals differing in their appearance. As far as I know the literature, till now there is no analytical data published referring to these black and orange-red amphiboles and we have no reference in literature for Magnesiohornblende and Ferrohornblende respectively.
Because of that during the last years various collectors started to get their material probed.
Regarding my samples (red and black ones in the scoria from different localities) the black amphibole turned out to be Kaersutite. The orange-red amphibole has a smaller content of Titanium and is in composition close to the join Kaersutite / (Fluoro)-Magnesiohastingsite.
This information was added to the locality lists.
Christof

Christof - thank you for the clarification and information - I will change my image caption to "amphibole group" but, could it be kaersutite as well?

Yes, it could be kaersutite.

Without analysis I'll leave it as amphibole, note added to image caption

Remained 3 "magnesiohornblende" photos changed to amphibole.

Christoph: is the ferrohornblende in [www.mindat.org] reliably analysed?

Comment added to kaersutite page:

"Note: most kaersutites from the Eifel area (Germany) are probably not reliably identified (i.e., the identification was not based on quantitative chemical analyses and additional diffraction and spectroscopic analyses)."

Uve,

1. yes, but only quantitative chemical analyses

2. do you have new news regarding these amphiboles ?
some time ago you wrote: “Günter Blass, THE Eifel specialist, kindly asked me to write that these amphiboles are "definitely kaersutite" ".



Edited 1 time(s). Last edit at 12/05/2010 06:33AM by Christof Schaefer.

Thanks, Christof (sorry for misspelling your first name).

2. No. I am not aware of any published EMP analyses of the amphiboles in voids. SEM-EDS is not enough for a correct ID, even with modern machines and software.

The identification of the amphiboles has been done by EMP analyses,
but they are still not published.
I have removed all my entries with unpublished references.
Hope this will help to avoid further misunderstandings.

After this discussion I have reexamined the analyses, made in October 1995, from orange-brown needles from Eicher Sattel,
Andernach, Germany.

Powder XRD (thanks Thomas Felkel, Currenta, Leverkusen) corresponds with the calculated d-lines from kaersutite at
'mineralienatlas.de'.

ESD (non standardised) also corresponds the best with kaersutite: Na/K=2/ 1; Mg/Fe=8/ 1;Al/Si=1/ 3
Some measered peakheights diverges, without ZAF-correction: (Na,K)/Ca=1.1/ 2; (Mg,Fe)/Ca=4.4/ 2; Ti/Ca=0.8/ 2;
(Si,Al)/Ca=12/ 1
But as non specialist I've heard the low energy-peaks are higher, that would explain the deviation.

Greetings
Milo

PXRD and non-standardised SEM-EDS are unfortunately not enough for an unambiguous identification of such amphiboles. But at least the data show that you might have either kaersutite or a closely related amphibole member.

Just out of curiosity, are these now generally accepted as kaersutites?



Olav