Figure F72. Veins of anhydrite and pyrite together with Type 1 disseminated pyrite in highly altered dacite. The altered fragments are compositionally zoned with a silica-rich rim and clay-and anhydrite-rich interior. Note the absence of pyrite in the silicified rim and the zonal arrangement of very fine pyrite within the fragment at bottom right (Sample 193-1188A-7R-2 [Piece 2, 39-41 cm] in plane-polarized transmitted light; width of view = 0.275 mm. Photomicrograph ID# 1188A

Figure F72. Veins of anhydrite and pyrite together with Type 1 disseminated pyrite in highly altered dacite. The altered fragments are compositionally zoned with a silica-rich rim and clay-and anhydrite-rich interior. Note the absence of pyrite in the silicified rim and the zonal arrangement of very fine pyrite within the fragment at bottom right (Sample 193-1188A-7R-2 [Piece 2, 39-41 cm] in plane-polarized transmitted light; width of view = 0.275 mm. Photomicrograph ID# 1188A_1; thin section 6).