Any of various dark gray sandstones that contain shale.
A nonporous, dark-colored sandstone containing angular particles of other rocks.
A fine-grained conglomerate resembling sandstone.
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.
Origin of graywacke
- Partial translation of German Grauwacke grau gray Wacke rock (from Middle High German) (from Old High German waggo boulder wegh- in Indo-European roots)
From American Heritage Dictionary of the English Language, 5th Edition