sedimentary

Shale

Shale (Lutite)

Hardness: 3 on Mohs scale; Color: Gray to olive-gray; Luster: Dull/Earthy; Crystal structure: Microcrystalline (clay minerals); Cleavage: Fissile (splits into thin layers); Specific Gravity: 2.4-2.8

Hardness: 3 on Mohs scale
Color: Gray to olive-gray
Luster: Dull/Earthy

Identified May 26, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Gray to olive-gray; Luster: Dull/Earthy; Crystal structure: Microcrystalline (clay minerals); Cleavage: Fissile (splits into thin layers); Specific Gravity: 2.4-2.8

Formation & geological history

Formed through the compaction and lithification of silt and clay-sized mineral particles, typically in low-energy environments like lake beds or deep ocean floors over millions of years.

Uses & applications

Raw material for the production of brick, tile, and pottery. Occasionally used in cement manufacture and as a source for natural gas and oil in energy industries.

Geological facts

Shale is the most common sedimentary rock on Earth, making up an estimated 70% of the sedimentary crust. It often contains well-preserved fossils due to its fine-grained nature.

Field identification & locations

Identify by its fine grain and tendency to break into thin, flat sheets (fissility). Commonly found in areas with ancient inland seas or deltaic deposits. Collectors look for shale layers containing fossil imprints.