Figure F19. Angular brown to black (tachylitic) pyroclastic debris with local microlitic and vesicular textures (Sample 173-1068A-7R-2, 82 cm). A biotite fragment is present in the upper right corner of the field of view. These grains are set in a slightly birefringent matrix of clay minerals that could be altered fine ash. A. Plane-polarized light. B. Cross-polarized light.

Figure F19. Angular brown to black (tachylitic) pyroclastic debris with local microlitic and vesicular textures (Sample 173-1068A-7R-2, 82 cm). A biotite fragment is present in the upper right corner of the field of view. These grains are set in a slightly birefringent matrix of clay minerals that could be altered fine ash. A. Plane-polarized light. B. Cross-polarized light.