DescriptionDacite (Tertiary; Mt. General, San Bernardino County, California, USA) 15.jpg
English: Dacite from the Tertiary of California, USA.
Dacite is an extrusive igneous rock intermediate in composition between andesite and rhyolite. It has a crystalline texture and is usually porphyritic. The phenocrysts in this sample are moderately small and include quartz (= glassy gray), plagioclase feldspar (= white), and biotite mica (= black).
Locality: Mt. General, Mojave Block, San Bernardino County, southern California, USA
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