Dear all,
please find attached a photograph of a light-colored mineral that I found precipitated along multiple fractures in thin section. The mineral is generally elongated orthogonal to the fractures, which probably indicates the mineral grew along an extensional crack. Please note that the base of each photograph is ca. 1 mm. View in non-polarized light to the left and in polarized light to the right.
Thank you very much in advance! :)
All the best,
Jean-Baptiste
Looks like it could be a zeolite to me based general appearance, birefringence etc.
Bob H
Dear Mr. Koehl,
can you check the refractive indices relative to the surrounding minerals and provide further optical details. And first and foremost, where did you take the sample from ? By providing this information you can reduce the field of speculation.
Best regards
H.G.Dill
Hii Mr. Koehl,
What is the surrounding rocks, in which fracture developed ??
With best regards, Sagar
This is a sample of fault-rock in northern Norway. I think this particular one is from a fault zone in granodioritic gneiss. Nevertheless it seems that the lithology of the hostrock does not matter much in this case since we found these minerals along numerous fault zones that cut through very different lithologies (gabbros, granite, mafic-felsic gneisses, etc.). Thanks a lot for your time and help! :)
Dear Mr. Koehl,
you mention the mineral to be hosted by a fault zone. The only thing which is for sure is that the mineral formed post-kinematically and the birefringence lies between 0.005 and 0.010. There are numerous minerals fulfilling these requirements. All other attempts to determine the mineral means poking around in the fog because of lacking proper information on the optical data of the mineral. Please try and determine these data by a careful examination under the petrographic microscope.
Best regards
H.G.Dill
Its better to do EPMA analysis, in that thin polished section of ur sample..
With Best regards,
Sagar
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