A low-grade orthogneiss, sample 80MW0004 is
composed of K-feldspar (35%), plagioclase (32%), quartz (20%), biotite
(2%), oxides (1%), and trace muscovite. This rock appears to be
unmetamorphosed in hand sample, yet thin section examination shows minor
recrystallization, metamorphic textures, and grain size variation.
Biotite grains define a weak foliation. Twinning is common in all
feldspars. Plagioclase shows slight alteration to sericite/muscovite.