sedimentary
Shale / Mudstone
Sedimentary rock (Claystone / Mudstone / Shale)
Hardness: 2.5-3 on Mohs scale; Color: Grey, brownish-grey, dark grey; Luster: Dull, earthy; Grain size: Fine-grained, microcrystalline; Texture: Fissile to massive
- Hardness
- 2
- Color
- Grey, brownish-grey, dark grey
- Luster
- Dull, earthy
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Physical properties
Hardness: 2.5-3 on Mohs scale; Color: Grey, brownish-grey, dark grey; Luster: Dull, earthy; Grain size: Fine-grained, microcrystalline; Texture: Fissile to massive
Formation & geological history
Formed by the compaction and lithification of silt and clay minerals in low-energy environments such as river deltas, lake beds, or deep marine basins over millions of years.
Uses & applications
Used in the production of brick, tile, and Portland cement; historically and commercially important as a source rock for hydrocarbons (natural gas and oil).
Geological facts
Shale is the most abundant sedimentary rock on Earth, accounting for over half of all sedimentary rocks in the geologic record.
Field identification & locations
Identified in the field by its soft, fine-grained texture, earthy smell when wet, and tendency to split into thin layers (fissility). Common globally in sedimentary basins.
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