noun Etymology: partial translation of German Grauwacke Date: 1811 a coarse usually dark gray sandstone or fine-grained conglomerate composed of firmly cemented fragments (as of quartz or feldspar)
GRAYWACKE
Meaning of GRAYWACKE in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012