Sample of a columnar, dense flow of chrysophyric hyalobasanite. The phenocrysts are fresh, euhedral olivine crystals. The groundmass consists of a brownish glass in a state of devitrification containing small grains of olivine, augite, plagioclase, and magnetite. Many secondary growths of chalcedony and zeolite occur throughout the glass.
Geology and petrology of the Pribilof Islands, Alaska