sedimentary
Shale (or Mudstone)
Laminose Mudrock (composition: clay minerals, quartz, and mica flakes)
Hardness: 3 on Mohs scale; Color: Gray, brown, or charcoal; Luster: Dull/Earthy; Structure: Clastic with visible fissility (splitting into thin layers); Cleavage: Perfect along bedding planes.
- Hardness
- 3 on Mohs scale
- Color
- Gray, brown, or charcoal
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Gray, brown, or charcoal; Luster: Dull/Earthy; Structure: Clastic with visible fissility (splitting into thin layers); Cleavage: Perfect along bedding planes.
Formation & geological history
Formed through the lithification of clay and silt-sized particles deposited in slow-moving water environments like floodplains, lagoons, or deep ocean basins. Generally found in Paleozoic to Cenozoic sedimentary basins.
Uses & applications
Raw material for the production of brick, tile, and cement. Often serves as a source or reservoir rock for natural gas and petroleum (shale gas).
Geological facts
Shale accounts for approximately 70% of the sedimentary rock in the Earth's crust. It is the most common rock involved in the hydraulic fracturing process for energy extraction.
Field identification & locations
Identify by its ability to split into thin, flat sheets (fissility) and its soft, clay-like texture when wet. Commonly found in road cuts or stream banks in regions with sedimentary bedrock.
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