Advanced Search
Porphyritic Granite
Place Collected:Mount Washington, New Hampshire
Object number: BILLINGS-MW-L-8
DescriptionCoarse porphyritic granite composed of light and dark micas (≤ 2 mm), quartz (≤ 2 mm), and plagioclase phenocrysts (≤ 1.1 cm). Some plagioclase crystals have carlsbad twins.