sedimentary

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)

AI-generated identification · may be incorrect

Hardness: 2-3 Mohs. Color: Dark grey, charcoal, brownish-grey. Luster: Dull to earthy. Cleavage/Fissility: Exhibits fine layering and splitting along thin bedding planes. Texture: Fine-grained.

Hardness: 2-3 Mohs
Color: Dark grey, charcoal, brownish-grey
Luster: Dull to earthy

Identified July 27, 2026More sedimentary →

Explore Shale (or Mudstone/Siltstone) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 2-3 Mohs. Color: Dark grey, charcoal, brownish-grey. Luster: Dull to earthy. Cleavage/Fissility: Exhibits fine layering and splitting along thin bedding planes. Texture: Fine-grained.

Formation & geological history

Formed from the compaction and consolidation of fine-grained clay and silt sediments deposited in low-energy aquatic environments such as lakes, river deltas, and deep marine basins over millions of years.

Uses & applications

Used primarily as a raw material in the manufacture of brick, tile, and Portland cement, and historically studied as a source rock for hydrocarbons (oil and natural gas).

Geological facts

Shale is the most abundant sedimentary rock on Earth, making up over half of the entire sedimentary rock record.

Field identification & locations

Can be identified in the field by its fine-grained texture, dark color, and tendency to break into flat, thin layers (fissility). Common globally in sedimentary basins.