pla·​gio·​clase | \ ˈplā-j(ē-)ə-ˌklās How to pronounce plagioclase (audio) , ˈpla-, -ˌklāz\

Definition of plagioclase

: a triclinic feldspar especially : one having calcium or sodium in its composition

Examples of plagioclase in a Sentence

Recent Examples on the Web

It’s mostly made of plagioclase, a rock formed out of molten magma. Brian Resnick, Vox, "How Apollo moon rocks reveal the epic history of the cosmos," 15 July 2019 Apollo 11 samples showed that the lunar highlands (bright, high-standing regions as opposed to the dark lunar maria in low-lying areas) contain high concentrations of the mineral plagioclase. Erica Jawin, Scientific American, "Apollo’s Bounty: The Science of the Moon Rocks," 2 July 2019 Your average Hood plagioclase crystal that formed 21,000 years ago might have spent only 1-12% of its entire history, a few hundred to a few thousand years, in conditions that would have allowed eruption of the magma (think: hot). Erik Klemetti, WIRED, "The Ephemeral Nature of Magma Prior to Eruption," 17 Feb. 2014

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'plagioclase.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of plagioclase

circa 1868, in the meaning defined above

History and Etymology for plagioclase

Greek plagios oblique + klasis breaking, from klan to break — more at clast

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Last Updated

29 Jul 2019

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Time Traveler for plagioclase

The first known use of plagioclase was circa 1868

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More from Merriam-Webster on plagioclase Encyclopedia article about plagioclase

Comments on plagioclase

What made you want to look up plagioclase? Please tell us where you read or heard it (including the quote, if possible).


not constant or steady

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