Definition of "anorthite" []

• A rare plagioclase feldspar with high calcium oxide content occurring in igneous rocks. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Like labradorite and anorthite, it is a common constituent of basic igneous rocks, such as gabbro and basalt."
• "In chemical composition and in optical and other physical characters it is thus much nearer to the anorthite end of the series than to albite."
• "The name was afterwards applied by G. Tschermak to those plagioclase felspars which lie between labradorite and anorthite; and this has been generally adopted by petrologists."