![57.1 Metabasalt (“greenstone”). Nicasio Reservoir, Marin County, California. A few dark green augite and white plagioclase phenocrysts are the only visible grains in this fine-grained to aphanitic metavolcanic rock. [Scale shows mm and cm divisions.]](../57.1.JPG)
57.1 Metabasalt (“greenstone”). Nicasio Reservoir, Marin County, California. A few dark green augite and white plagioclase phenocrysts are the only visible grains in this fine-grained to aphanitic metavolcanic rock. [Scale shows mm and cm divisions.]