Fig. 11. Left side . Plagioclase crystal (center; tan) replaced in its core by microcline (gray; grid-twinned). Albite twinning of the grid-twinning in the microcline is parallel to the albite twinning of the plagioclase. Quartz adjacent to the plagioclase (orange, yellow, cream gray, and white). Right side. Plagioclase (light gray) replaced in the interior by irregular islands of microcline (dark gray). Quartz (white, gray, black). Biotite (brown). The plagioclase grain (whitish gray) has lost its normal zoning and albite twinning. Most nearby plagioclase grains lack these microcline islands.