groundmass

[ ground-mas ]

noun
  1. the crystalline, granular, or glassy base or matrix of a porphyritic or other igneous rock, in which the more prominent crystals are embedded.

Origin of groundmass

1
First recorded in 1875–80; ground1 + mass

Words Nearby groundmass

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024

How to use groundmass in a sentence

  • The felted or hyalopilitic texture is the most common, and plagioclase is the principal groundmass constituent.

    Mount Rainier | Various
  • In a basal flow in Moraine Park, the slaggy and compact phases show differences in phenocrysts as well as in groundmass.

    Mount Rainier | Various
  • These lavas have groundmass textures that vary from almost holo-crystalline to glassy.

    Mount Rainier | Various
  • Pyroxene, quartz and augite form the groundmass, as seen in section.

    The Long Labrador Trail | Dillon Wallace

British Dictionary definitions for groundmass

groundmass

/ (ˈɡraʊndˌmæs) /


noun
  1. the matrix of igneous rocks, such as porphyry, in which larger crystals (phenocrysts) are embedded

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012