Figure F55. Photomicrographs (both in plane-polarized light) of altered mafic phenocrysts (probably clinopyroxene). A. Trachyandesite of Unit 18 (Sample 183-1139A-71R-1, 0-6 cm). B. Trachyte of Unit 19 (Sample 183-1139A-73R-3, 37-39 cm).