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2017 Word of the Year

groundmass

[ground-mas] /ˈgraʊndˌmæs/
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
1875-1880
First recorded in 1875-80; ground1 + mass
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for groundmass
Historical Examples
  • Pyroxene, quartz and augite form the groundmass, as seen in section.

    The Long Labrador Trail Dillon Wallace
  • These lavas have groundmass textures that vary from almost holo-crystalline to glassy.

    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
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
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