Figure 41. Photomicrograph in plane-polarized light illustrating cristobalite-clay alteration (colorless patches) of pale brown volcanic glass in a moderately altered volcanic rock from Site 1191 (interval 193-1191A-2R-2, 103–106 cm). Note that microlitic plagioclase and magnetite (fine opaque spots) are unaffected by the alteration (field of view = 0.7 mm).