Greywacke
//ˈɡɹeɪ.wæk// noun
noun ·Rare ·Advanced level
Definitions
Noun
- 1 A hard dark sandstone with poorly sorted angular grains of quartz, feldspar, and small rock fragments in a compact, clay-fine matrix. countable, uncountable
"Endless bleak, rounded hills composed of shales and ribs of tough ‘greywackes’ make up the Southern Uplands – all of such rocks were originally deposited under marine conditions."
Example
More examples"Endless bleak, rounded hills composed of shales and ribs of tough ‘greywackes’ make up the Southern Uplands – all of such rocks were originally deposited under marine conditions."
Etymology
Anglicised form of grauwacke.
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Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.