Figure F33. A xenolithic fragment of volcanic rock embedded in the microlite-rich groundmass of Unit 72. The xenolith consists of very fine grained quartz and clay minerals and contains an aggregate of mosaic quartz crystals that probably represent an amygdule. Arrow = the enclosing volcanic groundmass is occupied by abundant, aligned plagioclase microlites, which wrap around the margin of the xenolith (interval 193-1188F-43Z-1, 67-69 cm; width of view = 5.5 mm. Photomicrograph ID# 1188F_111; thin section 111).