Noritic Hornblende Gabbro
Field Collector: Esper Signius Larsen Jr.
Place Collected:San Luis Rey Quadrangle, Southern California
Object number: ROC21753
DescriptionPlutonic medium-grained (1-5 mm) igneous rock. Salt-and-pepper coloration on a fresh surafce heavy on the pepper and light brown on weathered surface. Consists of black hornblende ~45% (up to 1 cm but ~5 mm on average), white-grey plagiocalse ~50% (~2 mm), and 5% augite (according to Larsen's analysis).