Fig. 15. Microcline (dark gray, upper left) penetrates and replaces plagioclase (center, light gray to white; partly altered to clay, tan, right side and bottom). Angular parts of plagioclase that project into microcline are myrmekitic, containing tiny quartz vermicules. Ghost remnants of incompletely replaced plagioclase continue into the microcline in a light-gray pattern beyond the longer myrmekite projection. From Cape Ann granite in Massachusetts, USA.