nAnorthosite(Petrol) A granular igneous rock composed almost exclusively of a soda-lime feldspar, usually labradorite.
Century Dictionary and Cyclopedia
nanorthositeIn petrography, a granular or gneissoid igneous rock of eastern Canada, consisting chiefly of the plagioclase feldspar, labradorite. The name (first used by Hunt in 1863) is now applied to rocks composed largely of any lime-soda feldspar (plagioclase). The anorthosites are regarded by some petrographers as the highly feldspathic extreme of the gabbro family of igneous rocks.
Webster's Revised Unabridged Dictionary
F. anorthose, triclinic feldspar (fr. Gr. priv. + straight) + -ite,
Anorthosite, mouth of the Seine river, Bad Vermilion lake, Ontario, Canada.
"Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 4" by Various