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Fused Granodiorite
Field Collector: Esper Signius Larsen Jr.
Place Collected:Cerro de la Calavera, San Luis Rey Quadrangle, California
Object number: ROC21715
DescriptionPorphyritic igneous rock that is black with anhedral white plagioclase phenocrysts. This rock consists of 70% black groundmass composed of black glass and 30% off-white plagioclase phenocrysts. This rock is thought to have formed from the melting of a granodiorite under very ideal conditions, it was already close to the surface (cool) when encompased by an andesite intrusion, and there was a lot of water involved according to Larsen and Switzer (1939).
In Collection(s)