![26.1 Vesicular porphyritic basalt. Hat Creek-Mt. Lassen area, California. The large vesicles and rectangular white plagioclase crystals are the most obvious features of this basalt, but some tiny augite (?) phenocrysts also are present in the gray, aphanitic groundmass. [Scale shows cm divisions.]](../26.1.JPG)
26.1 Vesicular porphyritic basalt. Hat Creek-Mt. Lassen area, California. The large vesicles and rectangular white plagioclase crystals are the most obvious features of this basalt, but some tiny augite (?) phenocrysts also are present in the gray, aphanitic groundmass. [Scale shows cm divisions.]