sedimentary

Shale

Shale (Fine-grained clastic sedimentary rock)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Gray to dark gray; Luster: Dull or earthy; Crystal Structure: Non-crystalline (fine-grained matrix); Cleavage: Perfect fissility (splits into layers); Specific Gravity: 2.4-2.8

Hardness: 3 on Mohs scale
Color: Gray to dark gray
Luster: Dull or earthy

Identified July 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the compaction of silt and clay-sized mineral particles, commonly referred to as mud. This usually occurs in low-energy environments like lake bottoms, river deltas, and floodplains over millions of years.

Uses & applications

Mainly used in the manufacture of cement, brick, and tile. It is also a significant source of natural gas and petroleum when it contains high organic content (oil shale).

Geological facts

Shale is the most common sedimentary rock on Earth, making up approximately 70% of the sedimentary rock in the Earth's crust. It often contains fossils of marine life or plants.

Field identification & locations

Identify by its fine-grained texture and its tendency to break along thin laminations or parallel layers (fissility). It is found globally in sedimentary basins. For collectors, look for layers that may contain fossil imprints.