Definition of greywacke in English:


(US graywacke)


  • [mass noun] A dark coarse-grained sandstone containing more than 15 per cent clay.

    ‘a 120-foot pyramid of battered greywacke a quarter mile offshore’
    [count noun] ‘the shales and greywackes of the Skiddaw Group’
    • ‘The Southern Highland Group, consisting of greywacke, shale, limestone and volcanic rock, forms the top of the Dalradian succession.’
    • ‘Geologically the axes from the New Guinea Highlands comprise thermally metamorphosed basalt, chert and greywacke depending on quarry source.’
    • ‘The builders used greywacke from the Rangitata River and limestone brought from Mount Somers and shaped the rocks by hand.’
    • ‘Higher vapour pressures would be generated in sediments of low permeability, such as mudstones, which would account for sills being more commonly found in shale and greywacke.’
    • ‘The rocks typically comprise a monotonous sequence of greywackes, reddish-weathering arkosic sandstones, shales and subordinate conglomerates.’


Late 18th century (as grauwacke): from German Grauwacke, from grau grey + wacke. The anglicized form dates from the early 19th century.