Fig. 13. Muscovite-biotite granodiorite showing possible muscovite (bright colored crystal) replacement of biotite (brown stringers and patches). To the left of the muscovite is an area in which microcline (dark gray) has replaced portions of a large plagioclase crystal which extends above the muscovite-biotite crystal. Remnant islands of plagioclase in the microcline are optically parallel to the larger plagioclase crystal. The plagioclase has been partly altered to sericite and clay. A portion of a zoned plagioclase crystal (right side, white) has a sericitized core (tan).