Fig. 21. Parallel aligned albite-twinned plagioclase patches (light gray) in microcline (black), making the microcline perthitic. The patches are remnants of a former plagioclase crystal that once filled this space. Some plagioclase patches contain tiny quartz blebs (white). Quartz (white, light gray; top right and top left). Pyramid Peak granite west of Lyons Lake. Thin section 166 from Loomis collection.