Figure F30. Close-up photomicrograph in plane-polarized light of gypsum (brown) partly replacing anhydrite (clear with cleavage), which has partially replaced altered volcanic clasts (upper half). The disseminated opaque grains are pyrite. (Section 193-1189B-2R-1 [Piece 2, 11-14 cm]; width of view = 1.38 mm. Photomicrograph ID# 1189B

Figure F30. Close-up photomicrograph in plane-polarized light of gypsum (brown) partly replacing anhydrite (clear with cleavage), which has partially replaced altered volcanic clasts (upper half). The disseminated opaque grains are pyrite. (Section 193-1189B-2R-1 [Piece 2, 11-14 cm]; width of view = 1.38 mm. Photomicrograph ID# 1189B_25, thin section 115).