Figure F7. Network of cristobalite-anhydrite-(pyrite) veins in altered dacite host portion of Sample 193-1188A-7R-2 [Piece 1, 17–21 cm]; CSIRO 142652). Layers of tiny pyrite grains define the Liesegang-like alteration of a former, possibly perlitic glass. Low birefringence clay replacing the glass has a plumose structure extending across these layers. Width of view = 5.0 mm; (A) ordinary light, (B) crossed polarizers.

Figure F7. Network of cristobalite-anhydrite-(pyrite) veins in altered dacite host portion of Sample 193-1188A-7R-2 [Piece 1, 17–21 cm]; CSIRO 142652). Layers of tiny pyrite grains define the Liesegang-like alteration of a former, possibly perlitic glass. Low birefringence clay replacing the glass has a plumose structure extending across these layers. Width of view = 5.0 mm; (A) ordinary light, (B) crossed polarizers.