Shale
Mineral NameShale
Chemical FormulaVariable (primarily clay minerals like illite, kaolinite, smectite, and quartz)
Mohs Hardness2.5
Streak ColorGray, brown, black (variable)
CleavageFissility (splits into thin layers along bedding planes)
FractureUneven, splintery, platy
Specific Gravity2
Colorsgray, black, brown, red, green
TransparencyOpaque
Type LocalityGlobally widespread in sedimentary basins
Mineral GroupSedimentary rock (clastic)
Usessource of clay for ceramics and bricks, cement production, source rock for oil and natural gas (shale gas/oil)
Associated Mineralsclay minerals, quartz, feldspar, mica, calcite, dolomite, pyrite, organic matter
Raritycommon
Description
The image displays a dark, blocky fragment of shale, exhibiting subtle layering or fissility characteristic of its formation from compacted mud.
Geological Context
Shale is a fine-grained clastic sedimentary rock formed from the compaction of mud (silt and clay) in low-energy environments such as lakes, lagoons, and deep marine basins. It often preserves fossils and organic matter.
