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porphyroblast

American  
[pawr-fer-oh-blast] / ˈpɔr fər oʊˌblæst /

noun

plural

porphyroblasts

  1. Geology. metacryst.

porphyroblast Scientific  
/ pôr-fîr′ə-blăst′ /

  1. A large crystal that is surrounded by a finer-grained matrix in a metamorphic rock. Porphyroblasts form by the recrystallization of existing mineral crystals during metamorphism. They are analogous to phenocrysts in igneous rock.

Example Sentences

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A porphyroblast is a large crystal of a particular mineral surrounded by small grains.

From Textbooks • Jan. 1, 2017

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.