Figure F18. Photomicrograph in plane-polarized light of Sample 187-1155B-2R-1, 68-71 cm (see "Site 1155 Thin Sections"), showing the intersection of a calcite vein with palagonite. Silica and Fe oxyhydroxides line the edge of the calcite vein. Palagonite displays concentric zoning from cryptocrystalline to crystalline (smectite) toward the dendritic alteration front. The vertical fracture within the palagonite contains Fe oxyhydroxides and silica.