- Geology. a dark-gray coarse-grained wacke.
Origin of graywacke
1805–15; partly translation, partly adapted from German Grauwache; see wacke
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for greywacke
In Cornwall and Devonshire, the lead ore is found in veins in killas, a clay-slate passing into greywacke.
- any dark sandstone or grit having a matrix of clay minerals
C19: partial translation of German Grauwacke; see wacke
- 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.