porphyroblast
[ pôr-fîr′ə-blăst′ ]
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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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Words nearby porphyroblast
porphyrinogen, porphyrinuria, porphyritic, porphyrization, porphyrize, porphyroblast, porphyrogenite, porphyroid, porphyropsin, porphyry, porpoise
The American Heritage® Science Dictionary
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