porphyroblast
[ 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.
Words nearby porphyroblast
porphyrinogen, porphyrinuria, porphyritic, porphyrization, porphyrize, porphyroblast, porphyrogenite, porphyroid, porphyropsin, porphyry, porpoise
The American Heritage® Science Dictionary
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