sedimentary

Shale

Shale (Argillaceous sedimentary rock)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Dark grey to black; Luster: Dull or earthy; Crystal structure: Very fine-grained (clay minerals); Cleavage: Fissile (splits into thin layers); Specific gravity: 2.4 - 2.8

Hardness: 3 on Mohs scale
Color: Dark grey to black
Luster: Dull or earthy

Identified July 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the compaction of silt and clay-size mineral particles. These sediments typically accumulate in low-energy environments like lake bottoms, river deltas, and floodplains over millions of years.

Uses & applications

Used primarily in the production of cement, bricks, and tiles. Historically significant as a source rock for petroleum and natural gas (shale gas) via hydraulic fracturing.

Geological facts

Shale is the most common sedimentary rock on Earth. Because of its fine-grained nature, it often preserves fossils with incredible detail, including leaves and ancient marine life.

Field identification & locations

Identify by its dark color, earthy smell when wet, and its tendency to split along thin, parallel planes (fissility). It is found globally in sedimentary basins.