Shale
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Mineral NameShale
Chemical FormulaAluminosilicates, SiO2 (complex mixture)
Mohs Hardness2.5
Crystal Systemamorphous
Lusterdull
Streak ColorWhite to light grey
CleavageFissile (splits along bedding planes)
Fractureuneven
Specific Gravity2.4
Colorsdark grey, black, green, red, brown
Transparencyopaque
Type LocalityWorldwide
Mineral GroupSilicates (dominant constituent minerals)
Usessource of clay for ceramics, bricks, cement, oil and gas reservoirs
Associated Mineralsclay minerals, quartz, feldspar, micas, organic matter
Raritycommon
Description
A dark grey, crescent-shaped, fine-grained sedimentary rock with a dull luster, often exhibiting fissility.
Geological Context
Shale forms from the compaction of mud (silt and clay) in low-energy depositional environments such as lakes, river deltas, and deep marine basins, making it the most common sedimentary rock.
