anorthosite

American  

[an-awr-thuh-sahyt] / ænˈɔr θəˌsaɪt /

noun

Petrology.

1. a granular plutonic rock composed largely of labradorite or a more calcic feldspar.

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anorthosite British  

/ ænˈɔːθəˌsaɪt /

noun

1. a coarse-grained plutonic igneous rock consisting almost entirely of plagioclase feldspar

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anorthosite Scientific  

/ ăn-ôr′thə-sīt′ /

1. An igneous rock consisting almost entirely of plagioclase feldspar, especially the labradorite variety. Anorthosites have been identified among rock samples collected from the Moon.

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Other Word Forms

• anorthositic adjective

Etymology

Origin of anorthosite

1860–65; < French anorthose anorthoclase ( an- an- ¹ + Greek orthós straight) + -ite ¹

Example Sentences

These included gypsum, carbonates, basalts, dunite, and anorthosite.

From Science Daily • Apr. 8, 2026

There are currently only two operational mines on the island -- one gold mine in the south, and one for anorthosite, a rock containing titanium, on the west coast.

From Barron's • Feb. 14, 2026

This ferroan anorthosite - or molten rock - formed the moon’s surface.

From BBC • Aug. 21, 2024

It was a breccia containing a nugget of anorthosite that apparently crystallized 4.46 billion years ago.

From Washington Post • Apr. 21, 2022

Segregations of iron ores, such as ilmenite, usually with pyroxene or olivine, occur in association with some gabbro and anorthosite masses.

From Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 4 "G" to "Gaskell, Elizabeth" by Various