sedimentary
Fossiliferous Shale
Carbonaceous Shale (with potential plant/aquatic fossils)
Hardness: 3 (Mohs scale), Color: Dark grey to black, Luster: Dull/Earthy, Crystal structure: Fine-grained/Aphanitic, Cleavage: Fissile (splits into layers)
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Physical properties
Hardness: 3 (Mohs scale), Color: Dark grey to black, Luster: Dull/Earthy, Crystal structure: Fine-grained/Aphanitic, Cleavage: Fissile (splits into layers)
Formation & geological history
Formed in low-energy environments like lake bottoms, swamps, or deep ocean floors through the compaction of clay and organic matter. This specimen appears to contain organic imprints characteristic of the Paleozoic or Mesozoic eras.
Uses & applications
Primary source for oil and natural gas (oil shale), used in the manufacture of brick, tile, and Portland cement. Frequently collected by paleontologists.
Geological facts
Dark shale gets its color from high organic content (carbon). It is the most common sedimentary rock on Earth and often preserves delicate fossils that would be destroyed in more turbulent environments.
Field identification & locations
Identify by its dark color, fine grain, and tendency to flake into flat sheets. Look for textural anomalies on the surface that may indicate fossilized organic remains like leaves or shells.
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