Graywacke is a “dirty” sandstone distinguishable by its angular to subangular clasts and minor silt/mud content. It often hosts graded beds.

Rock group	Sedimentary
Origin	Clastic/detrital
Particle size (Wentworth)	0.0625 – 2 mm

Graywacke in Hand Sample

Silurian-aged graywacke (from Siccar Point!)
Ordovician-aged Martinsburg Formation graywacke
Turbidites from Patagonia

Graywacke in Thin Section

Graywacke, plane polars
Graywacke, crossed polars