Fig. 18. Carlsbad-twinned and zoned plagioclase crystal with speckled, sericite-altered core. Remnant end of the plagioclase crystal (center; right) occurs as an island in microcline (gray; right side) and is in optical parallel alignment with larger plagioclase crystal (left side). Myrmekite with tiny quartz vermicules occurs on corners of plagioclase projecting into microcline.