grauwacken.

1794 R. Kirwan Elements Mineral. (ed. 2) I. 235 Its [sc. argillite's] transitions are into..hornstone, grau-wacken, syenite, [etc.].

1800 R. Jameson Mineral. Sc. Isles xii. 193 Near to Mr Campbell's house, I observed the ardesia covered by grauwacken, and both apparently traversed with the same basalt vein.

1807 H. Davy in Philos. Trans. (Royal Soc.) 97 10 Grauwackè from North Wales.

1851 T. Wright & G. F. Richardson Introd. Geol. (new ed.) viii. 246 The species of gasteropods are much less abundant in the ancient grauwacke limestones than those of bivalved mollusca.

1878 Proc. Amer. Philos. Soc. 1877–8 17 319 The first [fossil] is from the Devonian (grauwacken), the other from the Carboniferous.

1907 Geogr. Jrnl. 30 194 The upper part of the Franz Josef glacier is bordered by argillites and grauwackes.

1931 Proc. Geologists' Assoc. 42 114 An irregular band..joining hands with the Grauwacke of the Vosges and the anthracitic deposits of the Alps.

1991 Jrnl. Hellenic Stud. 111 160 It [sc. a statue] is made of the dark greenish-gray stone called grauwacke, not found near Susa, though there were quarries in the region of the Wadi Hammamat.

2008 J. Verniers et al. in T. McCann Geol. Central Europe I. vi. 282/1 The Grauwacke Zone..extends over a great distance in a series of different nappes.