A sandstone of which the mud matrix in which the grains are embedded amounts to between 15 and 75 percent of the mass.
- ‘In the Western zone and the contiguous Hooper Complex, turbiditic quartz wacke was deposited on the Kimberley Craton between c. 1872 and 1865 Ma.’
- ‘Greywacke is an old term still sometimes used for a particular type of wacke especially in grey-coloured turbidite sequences.’
- ‘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 upper 300 m of the Haengefjeldet Formation is made up of 3-10 m thick well-sorted, normally graded, matrix-supported sandstones and wackes.’
- ‘The Annascaul Formation is at least 500 m thick, and is dominated by mudrocks with subordinate quartz wacke sandstones, tuffaceous fine conglomerates and melange.’
Early 19th century: from German, from Middle High German wacke large stone Old High German wacko pebble.