Anorthosite

A coarse-grained crystalline rock consisting mostly of calcic plagioclase (>90%, usually labradorite) with <10% mafics. The mafic mineral may be clinopyroxene, orthopyroxene, olivine, or, more rarely, amphibole. Oxides, mostly magnetite or ilmenite, are also common. The lunar highlands are composed predominantly of anorthosite.