greywacke
English
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Alternative forms
[edit]Etymology
[edit]Anglicised form of grauwacke.
Pronunciation
[edit]Noun
[edit]greywacke (countable and uncountable, plural greywackes)
- (geology) A hard dark sandstone with poorly sorted angular grains of quartz, feldspar, and small rock fragments in a compact, clay-fine matrix.
- 2004, Richard Fortey, The Earth, Folio Society, published 2011, page 177:
- 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.