from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A conspicuous, usually large, crystal embedded in porphyritic igneous rock.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. any relatively large crystal embedded in a more fine-grained or glassy igneous rock

from the GNU version of the Collaborative International Dictionary of English

  • n. One of the prominent embedded crystals of a porphyry.

from The Century Dictionary and Cyclopedia

  • n. One of the prominent crystals in a porphyritic rock.


pheno- + cryst(al).
(American Heritage® Dictionary of the English Language, Fourth Edition)


  • Fig. 9 (A, B) shows an MI believed to have formed as a two-phase mixed inclusion (melt + fluid) within a quartz phenocryst of peralkaline rhyolite (Lowenstern et al. 1991).

    Evidence for Fluid Saturation and Degassing

  • Quartz in groundmass does not appear to have nucleated directly on phenocryst, but is in optical continuity with it. (f) Primary vapor-rich fluid inclusion in phenocrystic quartz.


  • Radiating fringe of feldspar in groundmass is in optical continuity with phenocryst, from which it nucleated. (e) Quartz phenocryst is surrounded by feldspar groundmass.


  • Figure parts a-e with crossed nichols. (a) Micrographic groundmass surrounds feldspar phenocryst fragment. (b) Micrographic groundmass around clinopyroxene phenocryst.


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