graywacke

or grey·wacke

[ grey-wak, -wak-uh ]

noun

1. Geology. a dark-gray coarse-grained wacke.

graywacke

/ grā′wăk′,-wăk′ə /

1. 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.

Word History and Origins

Origin of graywacke¹

1805–15; partly translation, partly adapted from German Grauwache; wacke

Example Sentences

Appropriately pronounced a "secondary graywacke slate," by Mr. Eaton.

From Project Gutenberg

In the transition graywacke of the south of Scotland, the galena mines of Leadhills occur.

From Project Gutenberg

Their material, however, is not flint, but either graywacke or a kind of tough slate.

From Project Gutenberg

Is it primitive, or is it graywacke like Catskill Mountains?

From Project Gutenberg

I received a specimen of slaty graywacke from Lake Superior.

From Project Gutenberg