an·​or·​tho·​site ə-ˈnȯr-thə-ˌsīt How to pronounce anorthosite (audio)
: a granular plutonic igneous rock composed almost exclusively of a soda-lime feldspar (such as labradorite)
anorthositic adjective

Examples of anorthosite in a Sentence

Recent Examples on the Web The light-colored highlands are composed of anorthosite, an igneous rock believed to be the remains of the primordial crust of the Moon, and are dated to 4.5 to 3.9 billion years. David Bressan, Forbes, 10 Oct. 2021 At the moment, only two mines in Greenland are active, one producing rubies and the other anorthosite, used in paints, plastic coatings and special varieties of glass. New York Times, 1 Oct. 2021 Astronauts on Apollo 15 collected a 4 x 2-inch chunk of crystal anorthosite over 4 billion years old. Michael O’Donnell, WSJ, 2 July 2021 The chunks of anorthosite weren’t deposited there by nature — they were trucked in from the mountains around Pasadena. Los Angeles Times, 19 July 2019

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'anorthosite.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


French anorthose, a feldspar, from a- + Greek orthos — more at orth-

First Known Use

1863, in the meaning defined above

Time Traveler
The first known use of anorthosite was in 1863

Dictionary Entries Near anorthosite

Cite this Entry

“Anorthosite.” Dictionary, Merriam-Webster, Accessed 7 Dec. 2023.

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