graywacke

American  

[grey-wak, -wak-uh] / ˈgreɪˌwæk, -ˌwæk ə /

Or greywacke

noun

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

---

graywacke Scientific  

/ 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.

---

Etymology

Origin of graywacke

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

Example Sentences

They were carved from dark, matte graywacke, a favorite material for Egyptian sculptors.

From Washington Post

It is hard not to be mesmerized, for instance, by the larger-than-life-size head of Julius Caesar, carved from the same dark graywacke, quarried from the Egyptian desert, as the Boston Green Head.

From Washington Post

Externally the walls of the basement story are of gray marble relieved by bands of graywacke, those of the story above of white marble with similar bands, while the uppermost story is of white marble with checker-work pattern of oblong gray blocks, laid stair-fashion.

From Project Gutenberg

Graywacke, Greywacke, gr�′wak-e, n. a kind of sandstone, consisting of rounded pebbles and sand firmly united together.

From Project Gutenberg

Leaving our camp on the mountain side, at seven A.M. we set out for the summit of Ktaadn, traveling steadily up the slide, clambering over loose bowlders of granite, trap, and graywacke, which are heaped up in confusion along its course.

From Project Gutenberg