sedimentary

Shale with Plant Fossils / Carbonaceous Shale

Laminated Mudrock (Siliciclastic)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale (fairly soft/fissile); Color: Grey, black, or dark brown due to organic content; Luster: Dull/Earthy; Crystal structure: Non-crystalline (composed of clay and silt-sized particles); Fracture/Cleavage: Fissile, meaning it breaks easily into thin layers.

Hardness: 3 on Mohs scale (fairly soft/fissile)
Color: Grey, black, or dark brown due to organic content
Luster: Dull/Earthy

Identified March 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the slow deposition of silt and clay-sized mineral particles in low-energy environments like swamps, lake bottoms, or deep-ocean basins. The dark coloration and presence of plant-matter imprints suggest a swampy or flood-plain environment during the Carboniferous period (approx. 300 million years ago).

Uses & applications

Major source of natural gas and oil when processed; historically used in brickmaking and cement production; often collected by hobbyists for the plant fossils contained within the layers.

Geological facts

Shale is the most common sedimentary rock on Earth. This specific specimen appears to contain compressions of prehistoric flora, which helped form the great coal beds of the world during the Paleozoic era.

Field identification & locations

Identify in the field by its layered appearance and the fact that it splits into flat sheets when struck; it will not fizz with acid (distinguishing it from limestone). Commonly found in sedimentary basins worldwide, particularly near coal mines or river valleys.