Fig. 15. Albite- and Carlsbad-twinned plagioclase (black and cream, left side), which encloses an island of biotite (dark brown to black). Microcline (right side, gray) contains irregular stringers of plagioclase (tan) and remnant plagioclase islands (right of center and lower right), all of which are in optical parallel continuity with the adjacent plagioclase (left side)., The microcline has penetrated and replaced the plagioclase along albite-twin planes (left of center) and is pseudomorphic after a former euhedral plagioclase crystal that once filled this space as is indicated by the continuous extension of the plagioclase border to the microcline border (upper left). The projection of the plagioclase into the microcline (left of center) is myrmekitic.