1. A coarse-grained sedimentary rock composed of angular fragments of quartz, feldspar, and other minerals in a fine-grained matrix, typically gray in color.
Usage: geology; also spelled greywacke

Examples

• The cliff face exposed layers of graywacke dating back millions of years.
• Geologists identified the rock sample as graywacke based on its angular mineral fragments.
• Graywacke is commonly found in mountain ranges and ancient sedimentary basins.
• The construction company quarried graywacke for use as aggregate in concrete.
• This graywacke formation provides evidence of ancient turbidity currents on the ocean floor.