Figure F4. Slightly altered rhyodacite with volcanic groundmass that is unevenly altered to a very fine grained assemblage of silica and clay. (Sample 193-1191A-3R-1 [Piece 9, 51-54 cm] in plane-polarized light; width of view = 5.5 mm. Photomicrograph ID# 1191A

Figure F4. Slightly altered rhyodacite with volcanic groundmass that is unevenly altered to a very fine grained assemblage of silica and clay. (Sample 193-1191A-3R-1 [Piece 9, 51-54 cm] in plane-polarized light; width of view = 5.5 mm. Photomicrograph ID# 1191A_9; thin section 52).