Orthogneiss sample 82MW0012 contains a mineral
assemblage of K-feldspar (38%), plagioclase (35%), quartz (20%), biotite
(5%), and trace amounts of muscovite, oxides, sphene, epidote, and
chlorite. This rock is characterized by perthitic porphyroclasts of
K-feldspar (up to 8 mm) in a matrix of biotite and fine, hexagonal
grains of recrystallized quartz, plagioclase and K-feldspar. Large
sphene grains (up to 1.3 mm) are rimmed by muscovite and biotite.
Plagioclase shows albite twinning, seritization, and some antiperthite