noun[mass noun] Geology
A granular igneous rock composed largely of labradorite or another plagioclase.
- Because of the preponderance of the mineral anorthite (a calcium-rich variety of the mineral plagioclase feldspar) this rock type is called anorthosite.
- Coarse-grained anorthosite is the predominant rock type in these bodies.
- The plagioclase crystals would have formed subcircular lenses of anorthosite that punctuated background chromite accumulation.
Mid 19th century: from French anorthose 'plagioclase' + -ite1.
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