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 (grā′wăk′, -wăk′ə)
Any of various dark gray sandstones that contain shale.

[Partial translation of German Grauwacke : grau, gray + Wacke, rock (from Middle High German, from Old High German waggo, boulder; see wegh- in Indo-European roots).]
References in periodicals archive ?
Reference mix-design contained commonly used aggregate from around the city of Brno (Czech Republic): 0-4 mm quartz sand (Naklo), 4-8 mm carboniferous greywacke (Olbramovice) and 8 16 mm carboniferous graywacke (Olbramovice).
5,300-3,000 BCE) are cosmetic palettes, typically made from graywacke or slate.
Li and Horne [11] proposed a scaling equation for co-current imbibition of water into gas-saturated porous media (Berea, chalk, and Graywacke cores):