graywacke

[grey-wak, -wak-uh]

noun

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

We're sure to get the better of Graywacke, and why not anticipate?
A Summer in Leslie Goldthwaite's Life.
Mrs. A. D. T. Whitney
Is it primitive, or is it graywacke like Catskill Mountains?
Personal Memoirs Of A Residence Of Thirty Years With The Indian Tribes On The American Frontiers
Henry Rowe Schoolcraft

graywacke in Science

[grā′wăk′, -wăk′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.