Dictionary.com
definitions
  • synonyms
porphyroblast in Science

porphyroblast

[pôr-fîrə-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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

  • About
  • Cookies, Terms, & Privacy
© 2018 Dictionary.com, LLC.