3
votes
Accepted
What would a rock thin section look like without any polarizers?
It would look almost identical to the image obtained using plane-polarised light.
Some minerals would look darker, especially those with strong pleochroism such as biotites and amphiboles, because ...
- 23.3k
2
votes
Help with petrographic analysis of a complex mineral
It would help to be able to see photos with the stage at different points of rotation. However, this looks like a mafic volcanic rock with olivine being replaced by iddingsite in the top left; so ...
- 435
1
vote
Accepted
What do opaque rims on biotite in a volcanic rock mean?
There are several options.
During decompression, biotite is no longer stable and the hydrogen volatilises, leaving behind fine-grained intergrowth of oxide and silicate minerals.
Oxidation of the ...
- 23.3k
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