noun
- large crystals embedded in a finer-grained matrix in igneous rocks
Usage: geology; plural of phenocryst
Examples
- The granite contained large feldspar phenocrysts visible to the naked eye.
- Geologists identified quartz phenocrysts in the volcanic rock sample.
- The porphyry’s phenocrysts formed during slow cooling deep underground.
- Students examined the phenocrysts under a magnifying glass during field work.
- The size of the phenocrysts indicated the rock’s cooling history.
- Olivine phenocrysts gave the basalt a distinctive green appearance.