I recognise the cross-hatch of microcline, but I'm not sure of the minerals showing the bright interference colours (needless to say, I'm new to analysing thin sections).
I've added 2 photos showing the thin section in plane and cross polar light. Any help would be greatly appreciated, thank you.
The crystal aggregate with distinct cleavage (in the center of the picture), showing pale pinkish color (in plane polarized light), and blue to purple interference colors (between crossed polarizers), is white mica (muscovite).
The surrounding crystall aggregates with distinct cleavage, showing brownish colors (in plane polarized light) and various interference colors, like green, brown, orange (between crossed polarizers) are biotite, locally interspersed with dark pleochroic haloes (caused by U-Th-bearing inclusions).
Further more there are some partially altered plagioclase crystals (without any cross-hatch twinning), showing simple zoning, and a few colorless transparent quartz grains, as well as a few colorless transparent tiny apatite inclusions in biotite.
Best regards,
Guenter Grundmann
In your image (attached) I have marked the plagioclase with the letter "p", the quartz grains with the letter "q".
Please check if the grains marked with "p" are optically biaxial,
and please check if the grains marked with "q" are uniaxial.
Thank you and good luck.
Best regards,
Guenter Grundmann
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