![27.0 Vesicular, porphyritic olivine basalt. Locality is near Elko, Nevada. Large glassy green to black phenocrysts of olivine and a few white phenocrysts of plagioclase (one, on the far right, shows cleavage) scattered in the gray aphanitic matrix and among the numerous vesicles, characterize the rock. Sample courtesy of David Bero. [Scale shows cm divisions.]](../27.0.JPG)
27.0 Vesicular, porphyritic olivine basalt. Locality is near Elko, Nevada. Large glassy green to black phenocrysts of olivine and a few white phenocrysts of plagioclase (one, on the far right, shows cleavage) scattered in the gray aphanitic matrix and among the numerous vesicles, characterize the rock. Sample courtesy of David Bero. [Scale shows cm divisions.]