anorthosite

noun Petrology.

1. a granular plutonic rock composed largely of labradorite or a more calcic feldspar.

noun

1. a coarse-grained plutonic igneous rock consisting almost entirely of plagioclase feldspar

1. An igneous rock consisting almost entirely of plagioclase feldspar, especially the labradorite variety. Anorthosites have been identified among rock samples collected from the Moon.