anorthosite
noun
an·or·tho·site
ə-ˈnȯr-thə-ˌsīt 
: a granular plutonic igneous rock composed almost exclusively of a soda-lime feldspar (such as labradorite)
Examples of anorthosite in a Sentence
Recent Examples on the Web
The presence of anorthosite on the moon suggested that the entire orb was once a magma ocean, or completely molten.
—
Jackie Wattles, CNN Money, 6 Apr. 2026
Because of its high alumina content, anorthosite is used to produce fiberglass and as a sustainable, low-carbon source of aluminum.
—Ariel Cohen, Forbes.com, 20 Feb. 2026
Greenland has had nine different mines since World War II, but only one, for the mineral anorthosite, is active today.
—IEEE Spectrum, 8 May 2025
The discovery of anorthosite — an ancient type of rock formed from cooling molten lava — in the lunar highlands suggested that, early in its history, the Moon had vast magma oceans.
—Anna Nordseth, Discover Magazine, 29 Oct. 2024
Off Planet’s recipes combine several rocks, including anorthosite and basalt.
—Matthew Hutson, The New Yorker, 24 Sep. 2024
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
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Jackie Wattles, CNN Money, 6 Apr. 2026
Because of its high alumina content, anorthosite is used to produce fiberglass and as a sustainable, low-carbon source of aluminum.
—Ariel Cohen, Forbes.com, 20 Feb. 2026
Greenland has had nine different mines since World War II, but only one, for the mineral anorthosite, is active today.
—IEEE Spectrum, 8 May 2025
The discovery of anorthosite — an ancient type of rock formed from cooling molten lava — in the lunar highlands suggested that, early in its history, the Moon had vast magma oceans.
—Anna Nordseth, Discover Magazine, 29 Oct. 2024
Off Planet’s recipes combine several rocks, including anorthosite and basalt.
—Matthew Hutson, The New Yorker, 24 Sep. 2024
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
Cite this Entry
“Anorthosite.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/anorthosite. Accessed 22 Apr. 2026.
Copy CitationLove words? Need even more definitions?
Merriam-Webster unabridged
