Fig. 13. A normal-zoned, albite-twinned plagioclase grain (black to light tan) is broken parallel to twin planes and replaced by K-feldspar (microcline, lower part). At the right end of the microcline, the plagioclase (dark gray) adjacent to the microcline and abutting against plagioclase (white, light gray) is myrmekite, but the quartz vermicules are too tiny to see. Biotite (brown, lower left side). Core of plagioclase is slightly sericitized.