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Nodular Norite of the San Marcos Gabbro
Field Collector: Esper Signius Larsen Jr.
Place Collected:Near "Vista Grande" east of Vista, San Luis Rey Quadrangle, Southern Califronia.
Object number: ROC21761
DescriptionSalt-and-pepper medium-grained (-5 mm) plutonic igneous rock with cm sized regions of darker and lighter grey, the darker regions are the orbicular or nodular structures. Mineral modes for the matrix (non-nodular part) given by Larsen (1948) are 58% plagioclase, 22% hornblende, 7% quartz, 6% biotite, 3% augite (clinopyroxene), 3% hypersthene (orthopyroxene), and 1% Fe-ore (magnetite). Mineral modes for the nodule given by Lasen (1948) are 60% plagioclase, 17% augite, 10% hypersthene, 10% quartz, 2% Fe-ore, 1% hornblende, and 1% biotite.
In Collection(s)