sedimentary
Shale
Lutaceous Rock (Hydrous Aluminum Silicates)
Hardness: 3 on Mohs scale; Color: Gray to olive-green; Luster: Dull/Earthy; Structure: Fissile (layers easily); Cleavage: Perfect along bedding planes; Texture: Fine-grained.
- Hardness
- 3 on Mohs scale
- Color
- Gray to olive-green
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Gray to olive-green; Luster: Dull/Earthy; Structure: Fissile (layers easily); Cleavage: Perfect along bedding planes; Texture: Fine-grained.
Formation & geological history
Formed through the compaction and cementation of silt and clay-sized mineral particles, usually in low-energy environments like lake beds or deep ocean floors over millions of years.
Uses & applications
Primarily used in the construction industry for making bricks, cement, and tiles. It is also a significant source for fossil fuel extraction, specifically shale gas and oil.
Geological facts
Shale is the most common sedimentary rock on Earth, making up over 50% of the sedimentary rocks in the Earth's crust. It often contains well-preserved fossils due to its fine-grained nature.
Field identification & locations
Identify by its ability to split into thin, flat sheets (fissility). It will not fizz with acid like limestone. Common in basins worldwide; look for layered outcroppings near water sources.
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