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[grey-wak, -wak-uh] /ˈgreɪˌwæk, -ˌwæk ə/
Geology. a dark-gray coarse-grained wacke.
Origin of graywacke
1805-15; partly translation, partly adapted from German Grauwache; see wacke Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for graywacke
  • Primarily fine-grained pelitic rocks and graywacke, variably metamorphosed.
  • Schist and gneiss in alternating layers suggest a turbidite sequence of shale and graywacke.
  • The regolith weathered from gray and brown acid sandstone in places interbedded with shale and graywacke.
British Dictionary definitions for graywacke


any dark sandstone or grit having a matrix of clay minerals
Word Origin
C19: partial translation of German Grauwacke; see wacke
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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graywacke in Science
  (grā'wāk', -wāk'ə)   
Any of various dark gray, coarse-grained sandstones that contain abundant feldspar and rock fragments and often have a clay-rich matrix. Graywackes are thought to originate in environments where erosion, transportation, and deposition happen so quickly that minerals and rock fragments do not have sufficient time to break down into finer constituents.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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