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Andesite
Field Collector: Esper Signius Larsen Jr.
Place Collected:my best guess is near El Modena Corona Quadrangle, Southern California
Object number: Cor 38-55
DescriptionDark grey with a tinge of green porphyritic volcanic rock. Phenocrysts are plagioclase crystals (~2 mm) and pyroxene (~2 mm). In thin section, the phenocrysts of plagioclase are almost completely replaced by calcite and the pyroxene is replaced by chlorite. The groundmass is composed of plagioclase laths < 0.1mm.
In Collection(s)