groundmass
/ˈgrau̇n(d)-ˌmas/ (ame, mw)
groundmass — noun
1. in a porphyritic rock, the small-grained or glass-like material surrounding the
in a porphyritic rock, the small-grained or glass-like material surrounding the larger crystals you can see with the naked eye.
Under the microscope, Samir saw bright crystals of quartz set in a dark groundmass.
collocation: set in a (dark/fine) groundmass
The groundmass of this lava sample is so fine that it looks almost like glass.
pattern: the groundmass of [rock sample] is [texture]
Tariq's students learned to tell the large crystals from the surrounding groundmass.
In many volcanic rocks, the groundmass cooled quickly and never formed visible crystals.
Ife pointed at the pink feldspar grains floating in a pale grey groundmass.
- matrix
broader term used across petrology and sedimentology; groundmass is reserved for the fine material around phenocrysts.
- mesostasis
the very last material to crystallise between earlier crystals; a narrower technical subset of the groundmass.
- phenocryst
the large visible crystals embedded WITHIN the groundmass — the contrasting component, not the same field of view.
文法句型
the groundmass of [rock type]
用法筆記
Almost always uncountable and used in petrology or igneous-rock contexts. Subject of the surrounding sentence is usually a rock sample, thin section, or specimen rather than a person.