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porphyroblast
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porphyroblast

crystal
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Quick Summary

A porphyroblast is a large crystal within a metamorphic rock that is typically larger than the surrounding mineral grains. These crystals, such as garnet, can grow before, during, or after deformation of the rock. The study of porphyroblasts provides valuable information about the pressure and temperature conditions under which the rock formed and underwent deformation. In contrast, phenocrysts are large crystals found in igneous rocks, embedded in a finer-grained matrix.12

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4 Britannica Sources
  1. porphyroblast
  2. metamorphic rock - Major features
  3. igneous rock - Fabric
  4. granophyre

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