ground·​mass ˈgrau̇n(d)-ˌmas How to pronounce groundmass (audio)
: the fine-grained or glassy base of a porphyry in which the larger distinct crystals are embedded

Examples of groundmass in a Sentence

Recent Examples on the Web Can instances where the composition of melt in inclusions differs significantly from the composition of the groundmass surrounding the same crystal be evidence of mixing? Erik Klemetti, Discover Magazine, 22 Dec. 2010

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'groundmass.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

1879, in the meaning defined above

Time Traveler
The first known use of groundmass was in 1879

Dictionary Entries Near groundmass

Cite this Entry

“Groundmass.” Dictionary, Merriam-Webster, Accessed 25 Feb. 2024.

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