Figure F34. Perlitic cracking preserved in altered volcanic rock. The previously glassy rock now consists dominantly of microcrystalline quartz, and the fine, arcuate domains defining the perlitic cracks are occupied by chlorite and black, cryptocrystalline material (Sample 193-1189B-13R-1 [Piece 6, 34-36 cm]; width of view = 1.38 mm). A. Photomicrograph in plane-polarized light (Photomicrograph ID#1189B_63; thin section 128). B. Photomicrograph in cross-polarized light (Photomicrograph ID# 1189B

Figure F34. Perlitic cracking preserved in altered volcanic rock. The previously glassy rock now consists dominantly of microcrystalline quartz, and the fine, arcuate domains defining the perlitic cracks are occupied by chlorite and black, cryptocrystalline material (Sample 193-1189B-13R-1 [Piece 6, 34-36 cm]; width of view = 1.38 mm). A. Photomicrograph in plane-polarized light (Photomicrograph ID#1189B_63; thin section 128). B. Photomicrograph in cross-polarized light (Photomicrograph ID# 1189B_64; thin section 128).