porphyroblast

American

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

noun

porphyroblast Scientific

/ pôr-fîr′ə-blăst′ /

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.

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porphyroblast porphyroblasts

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

From Textbooks ● Jan. 1, 2017

Common minerals are muscovite, biotite, and porphyroblasts of garnets.

From Textbooks ● Jan. 1, 2017

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