sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
Hardness: 2-3 Mohs. Color: Dark grey, charcoal, brownish-grey. Luster: Dull to earthy. Cleavage/Fissility: Exhibits fine layering and splitting along thin bedding planes. Texture: Fine-grained.
- Hardness
- 2-3 Mohs
- Color
- Dark grey, charcoal, brownish-grey
- Luster
- Dull to earthy
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Physical properties
Hardness: 2-3 Mohs. Color: Dark grey, charcoal, brownish-grey. Luster: Dull to earthy. Cleavage/Fissility: Exhibits fine layering and splitting along thin bedding planes. Texture: Fine-grained.
Formation & geological history
Formed from the compaction and consolidation of fine-grained clay and silt sediments deposited in low-energy aquatic environments such as lakes, river deltas, and deep marine basins over millions of years.
Uses & applications
Used primarily as a raw material in the manufacture of brick, tile, and Portland cement, and historically studied as a source rock for hydrocarbons (oil and natural gas).
Geological facts
Shale is the most abundant sedimentary rock on Earth, making up over half of the entire sedimentary rock record.
Field identification & locations
Can be identified in the field by its fine-grained texture, dark color, and tendency to break into flat, thin layers (fissility). Common globally in sedimentary basins.
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