sedimentary
Shale
Shale (Sedimentary rock composed of mud/clay minerals)
Hardness: 3 on Mohs scale; Color: Black, dark gray, or charcoal; Luster: Dull or earthy; Crystal structure: Microcrystalline/clastic; Cleavage: Fissile (breaks into thin layers); Specific gravity: 2.4 - 2.8
- Hardness
- 3 on Mohs scale
- Color
- Black, dark gray, or charcoal
- Luster
- Dull or earthy
Identified More sedimentary →
Explore Shale in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3 on Mohs scale; Color: Black, dark gray, or charcoal; Luster: Dull or earthy; Crystal structure: Microcrystalline/clastic; Cleavage: Fissile (breaks into thin layers); Specific gravity: 2.4 - 2.8
Formation & geological history
Formed from the compaction and lithification of silt and clay-sized mineral particles, typically in low-energy environments like lake beds or deep ocean basins. Ages range from Precambrian to Cenozoic.
Uses & applications
Used in the production of bricks, tile, and Portland cement. It is also an important source of natural gas and oil when it contains organic matter (oil shale).
Geological facts
Shale is the most common sedimentary rock on Earth. It often contains well-preserved fossils because the fine-grained sediment protects small organisms from decay.
Field identification & locations
Identify in the field by its tendency to split into thin, flat sheets (fissility). It feels smooth but slightly gritty and will not fizz with acid unless it contains calcite.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary