wacke
/ˈwakə
/noun [mass noun] Geology
A sandstone of which the mud matrix in which the grains are embedded amounts to between 15 and 75 per cent of the mass.The rounded conglomerate pebbles consist of siltstone, mudstone, wacke, granophyric igneous rocks, and various intermediate to felsic volcanic rocks, set in a matrix rich in quartz and feldspar grains....
- The Annascaul Formation is at least 500 m thick, and is dominated by mudrocks with subordinate quartz wacke sandstones, tuffaceous fine conglomerates and melange.
- The upper 300 m of the Haengefjeldet Formation is made up of 3-10 m thick well-sorted, normally graded, matrix-supported sandstones and wackes.
Origin
Early 19th century: from German, from Middle High German wacke 'large stone', Old High German wacko 'pebble'.