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.
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).
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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