Definition of phenocryst in English:

phenocryst

Syllabification: phe·no·cryst
Pronunciation: /ˈfēnəˌkrist
 
/

noun

Geology
A large or conspicuous crystal in a porphyritic rock, distinct from the groundmass.
More example sentences
  • Pyroxene mineralogy evolves along two paths with near end-member hedenbergite phenocrysts in the groundmass and aegirine solid solution in miaroles.
  • Bulk tephra can include phenocrysts or xenocrysts, lithic fragments and other inclusions, the proportions of which may vary across the fallout area, making accurate correlation difficult.
  • The majority of the rhyolites are porphyritic and contain phenocrysts of one or more of the following: plagioclase, clinopyroxene, magnetite, quartz and sanidine, plus accessory apatite and zircon.

Origin

late 19th century: from French phénocryste, from Greek phainein 'to show' + krustallos 'crystal'.

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