Fig. 12. Left side. Plagioclase grains (cream, white, gray), some of which show mottled extinction under cross-polarized light. The dark gray plagioclase (top left) has remnant albite twinning. Several plagioclase crystals have been altered internally and have lost their albite twinning and normal zoning. Cores are An_25-30; rims are An_18-20. Quartz (cream, white). Right side . Plagioclase crystals (whitish gray) are speckled. Some have cores An_18-20; rims An_18-20. Others have reversed zoning with cores An₁₅; rims An_18-20. Some have tiny invisible islands of K-feldspar. See Fig. 3 in Collins (1997b). Biotite (brown); quartz (white).