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Magnesio-hornblende : ◻Ca2(Mg4Al)(Si7Al)O22(OH)2

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Copyright © Chinellato Matteo - Chinellatophoto.com
 
 
 
 
minID: 1DY-Y6H

Magnesio-hornblende : ◻Ca2(Mg4Al)(Si7Al)O22(OH)2

Copyright © Chinellato Matteo - Chinellatophoto.com  - This image is copyrighted. Unauthorized reproduction prohibited.
Field of View: 2.5 mm

2.5 mm group of magnesio-hornblende crystals. Collection Domenico Preite photo Matteo Chinellato

This photo has been shown 1031 times
Photo added:23rd Nov 2010
Dimensions:800x534px (0.43 megapixels)
Camera:CANON EOS 5D Mark II

Data Identifiers

Mindat Photo ID:348549 📋 (quote this with any query about this photo)
Long-form Identifier:mindat:1:4:348549:8 📋
GUID:e493dd91-dfb3-46f9-8401-d31d96468d4f 📋
Specimen MinID1DY-Y6H (note: this is not unique to this photo, it is unique to the specimen)

Discuss this Photo

PhotosMagnesio-hornblende, Montenero quarry

24th Apr 2020 08:46 UTCOlav Revheim Manager

Dear all. 

The hornblende from this locality has been analyzed and found to be magnsesio-hornblende. Consequently, the mineral name on all the photos uploaded as ferro-hornblende has been changed to magnesio-hornblende. Due to the large number of photos changed, I have chosen to give public notofication rather than contacting each of the photo uploaders. 

I hope that this method of notification is acceptable. 

Kind regards
Olav 

24th Apr 2020 09:21 UTCFrank K. Mazdab 🌟 Manager

While Marco is correct that the "hornblendes", particularly the Mg-rich ones, tend to be among the few amphiboles simple enough to be fairly definitively analyzed by EDS, it's still a bit unfortunate that the actual numerical data discussed in that 2010 thread at forum.amiminerals.it were not provided.

24th Apr 2020 23:39 UTCRalph S Bottrill 🌟 Manager

How many samples were analysed? I find amphiboles can vary considerably within a single crystal let alone throughout a rock.

25th Apr 2020 00:11 UTCFrank K. Mazdab 🌟 Manager

apparently two EDS spots on one of those little black crystals...

Olav posted the link to the discussion on the other related thread, but here it is again:

25th Apr 2020 06:41 UTCOlav Revheim Manager

I agree that we ideally would like to see a more thorough study and that it would be really beneficial to have the numerical data uploaded to mindat. 

That being said, I am happy to accept this ID at face value. First of all, there is an analysis of an amphibole done by someone (Marco E. Ciriotti) that actually knows what he is doing and how to interpret the results . We don't have too many of those. 

Also magnesio-hornblende is a common amphibole ( if the result was tschermakite, I would be more sceptical). A more thorough study would probably reveal more than one species  in the material, and chanches are that the majority of the material would then be labelled with the most exotic name. There are numerous examples of this practice. The result would then be more rather then less mis-labeled photos on mindat 

:-)

Olav 

25th Apr 2020 07:21 UTCFrank K. Mazdab 🌟 Manager

you're entirely correct, Olav. Marco does know what he's doing.

But given the breadth of the changes here that this new information resulted in, and recognizing that these changes have been made based literally on just two SEM-EDS analyses done on just one crystal (and unless that crystal was cross-sectioned, then further having been done on just one growth zone of that one crystal), it could certainly be argued that a more conservative approach to naming all these would be to simply label the samples, "hornblende root name". I know that doesn't have a very elegant sound to it... lol.

But on the other hand, as many specimens were formerly labeled "ferro-hornblende" and now have been changed, I suppose we can keep the new "magnesio-hornblende" moniker for now, and in the future they can certainly be changed again, if necessary.  :-)

25th Apr 2020 09:43 UTCRalph S Bottrill 🌟 Manager

Yes the term hornblende was a very handy one and most geologists and petrologists still use it widely for dark coloured amphiboles, but collectors are passionate about putting an exact name on a mineral specimen, even if there is a high probability of it being wrong. I shall continue to look at species names of amphiboles on Mindat with a high degree of scepticism!
 
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