Anorthosite from the Precambrian of California, USA. (~11.0 centimeters across at its widest)
Anorthosite is a coarsely-crystalline, intrusive igneous rock that is exclusively or dominantly composed of plagioclase feldspar (NaAlSi3O8 to CaAl2Si2O8). Its crystallinity ranges from phaneritic to pegmatitic and its color ranges from light to dark. Anorthosite is uncommon on Earth but is abundant on the Moon. Lunar anorthosites are light-colored, as is this sample from California's San Gabriel Mountains.
Geologic unit: San Gabriel Anorthosite Complex, Mesoproterozoic, ~1.2 Ga
Locality: undisclosed site in Soledad Canyon, western San Gabriel Mountains, Los Angeles County, southern California, USA
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