Figure F19. Photomicrographs showing striped areas thought to be pyroxene (olivine?) crystals replaced by clay minerals (Sample 198-1213B-32R-3, 72-75 cm). The "stripes" are likely shrinkage cracks produced when smectite alteration minerals were heated during thin section production. The cracks may mimic cleavage in the replaced mineral, which would favor a pyroxene precursor. Note that the crystals of opaque minerals exhibit skeletal textures. The upper view is in plane-polarized light, and the lower view is with nicols crossed.

Figure F19. Photomicrographs showing striped areas thought to be pyroxene (olivine?) crystals replaced by clay minerals (Sample 198-1213B-32R-3, 72-75 cm). The "stripes" are likely shrinkage cracks produced when smectite alteration minerals were heated during thin section production. The cracks may mimic cleavage in the replaced mineral, which would favor a pyroxene precursor. Note that the crystals of opaque minerals exhibit skeletal textures. The upper view is in plane-polarized light, and the lower view is with nicols crossed.