English

Alternative forms

• graywacke

Noun

greywacke ‎(countable and uncountable, plural greywackes)

1. (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 2011, p. 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.

Derived terms

• metagreywacke, metagraywacke

Translations