Mindat Logo

K-V mica

Posted by Corrado Balestra  
K-V mica
December 20, 2011 02:05PM
Hi everybody,
I have a question.
Is it possible in principle to classify as roscoelite an aluminum free K – V mica ?
I have just checked by EDX a mica with the above mentioned composition and I noticed that in the official formula for roscoelite KV3+2[(AlSi3)O10](OH)2 aluminum in the T4 site seems to be essential.
To be honest I hope to have a new mica member on hand...
Thanks in advance for your thoughts.

avatar Re: K-V mica
May 28, 2012 09:51PM
Vanadium dominance in the anion would not only make it a new species, but also a different compound type - a vanadosilicate (i.e. a V-Si heteropolyacid anion) as opposed to the alumosilicate (Al-Si heteropolyacid anion) in roscoelite. Also note that V3+ (unlike Al3+) is not easily incorporated in heteropolyacids (also, V(III) does not form homopolyacids on its own). If aluminium is really entirely missing, it is more likely that you have either an un-substituted silicate (and vacancies on the M+ site) or another element "substituting" (this is formally meant since you can't exchange a metal atom in the anion as you can with metal ions on a cation site) for aluminium. An IR spectrum will quickly tell you the situation in the anion - whether it is a pure silicate, whether it also contains Al-O groups and whether different M-O groups are present.
avatar Re: K-V mica
May 29, 2012 11:43AM
Thank you Peter.
The phase in under study.

Your Email:


  • Valid attachments: jpg, gif, png, pdf
  • No file can be larger than 1000 KB
  • 3 more file(s) can be attached to this message

Spam prevention:
Please, enter the code that you see below in the input field. This is for blocking bots that try to post this form automatically. If the code is hard to read, then just try to guess it right. If you enter the wrong code, a new image is created and you get another chance to enter it right.
Mineral and/or Locality  
Search Google  
Copyright © Jolyon Ralph and Ida Chau 1993-2014. Site Map. Locality, mineral & photograph data are the copyright of the individuals who submitted them. Site hosted & developed by Jolyon Ralph. Mindat.org is an online information resource dedicated to providing free mineralogical information to all. Mindat relies on the contributions of thousands of members and supporters. Mindat does not offer minerals for sale. If you would like to add information to improve the quality of our database, then click here to register.
Current server date and time: December 19, 2014 04:43:32
Mineral and Locality Search
and/or Locality:
Fade toolbar when not in focusFix toolbar to bottom of page
Hide Social Media Links
Slideshow frame delay seconds