porphyroblast
Large metamorphic crystal
A porphyroblast is a large crystal that grows within metamorphic rock, standing out conspicuously against the finer-grained matrix surrounding it.
Garnet porphyroblasts are common in schists.
The term distinguishes these crystals from phenocrysts, which form in igneous rocks from cooling magma rather than from metamorphic recrystallization.
Red semiprecious stone
- kyaniteBlue aluminosilicate mineral
- micaLayered silicate mineral
- gneissFoliated metamorphic rock
- schistPlaty-mineral metamorphic rock
amphibolite · facies · prograde · retrograde · foliation · pressure · temperature
Initial cluster formation
- growthIncrease in size
- matrixOrdered numerical arrangement
- groundmassRock's fine-grained foundation
- euhedralPerfectly faced crystal
anhedral · habit · morphology · lattice · overgrowth · zoning · inclusion · rotation
garnet
Red semiprecious stone
schist · amphibolite · facies · prograde · retrograde · foliation · pressure · temperature
nucleation
Initial cluster formation
- growthIncrease in size
- matrixOrdered numerical arrangement
- groundmassRock's fine-grained foundation
euhedral · anhedral · habit · morphology · lattice · overgrowth · zoning · inclusion · rotation · static
- rock featurescliff, cliff face, rock face, crag, overhang