Advanced Search
Bonsall Tonalite
Field Collector: Esper Signius Larsen Jr.
Place Collected:Near Bear Valley, San Luis Rey Quadrangle, CA
Object number: ROC21698
DescriptionPlutonic, medium grained (1-5 mm) igneous rock that is black and white on a fresh face. Consists of ~50% white plagioclase (~1-2 mm), ~20% black hornblende crystals (~0.5-1 cm), 15% black biotite crystals (~0.5 cm), and 15% light grey quartz (~1 mm).
In Collection(s)