[grey-wak, -wak-uh]
Geology. a dark-gray coarse-grained wacke.
Also, greywacke.

1805–15; partly translation, partly adapted from German Grauwache; see wacke Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
Cite This Source Link To gray-wacke
American Heritage
Science Dictionary
graywacke   (grā'wāk', -wāk'ə)  Pronunciation Key 
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.
Cite This Source
Copyright © 2014, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature