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

Graywacke, Plane Polars

Graywacke in plane polarized light. Magnification: 40x Click here to see graywacke in crossed polars: https://youtu.be/z94ywQWuTNE Click here to explore a ha…

Graywacke, Crossed Polars

Graywacke in cross polarized light. Magnification: 40x Click here to see graywacke rotating in plane polars: https://youtu.be/af4VFMA-oAU Click here to explo…