Shale

Shale is the protolith of slate.

Properties
Rock group Sedimentary
Origin Clastic
Particle size Wentworth ≤ 62.5 µm
Special properties Fissile; splits along
bedding planes

Shale in Hand Sample

Shale is often fossiliferous, frequently preserves sedimentary structures such as crossbedding and mudcracks, and comes in varying shades of grey, tan, black, and red.

Fossils in Millboro Formation shale from West Virginia

Mudcracks and raindrop impressions in a red shale

Graptolites in black shale

Shale in Thin Section

Laminated shale, plane polars

Laminated shale, crossed polars

Laminated shale, plane polars
Laminated shale, crossed polars