sedimentary
Shale
Laminated Mudstone (Shale)
Hardness: 3 on Mohs scale; Color: Gray, black, or brown; Luster: Dull/Earthy; Crystal structure: Non-crystalline (fine-grained clastic); Cleavage: Fissile (splits into thin sheets); Specific gravity: 2.4 - 2.8
- Hardness
- 3 on Mohs scale
- Color
- Gray, black, or brown
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Gray, black, or brown; Luster: Dull/Earthy; Crystal structure: Non-crystalline (fine-grained clastic); Cleavage: Fissile (splits into thin sheets); Specific gravity: 2.4 - 2.8
Formation & geological history
Formed through the compaction of silt and clay-sized mineral particles (mud) over millions of years, typically in low-energy environments like lake bottoms, river deltas, or floodplains.
Uses & applications
Used in the production of cement, brick, tile, and as a source rock for oil and natural gas (fracking). Often acts as a filler in various industrial applications.
Geological facts
Shale is the most common sedimentary rock on Earth, making up about 70 percent of the sedimentary rock in the Earth's crust. It is the primary rock type in which fossils are preserved.
Field identification & locations
Identify in the field by its tendency to split along thin, parallel planes (fissility). It feels smooth to the touch unlike sandstone and often smells earthy when wet. Common in riverbeds and road cuts.
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Shale or Slaty Mudstone
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