Shale

Shale is a fine-grained, clastic sedimentary rock, formed from mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite.[1] Shale is characterized by its tendency to split into thin layers (laminae) less than one centimeter in thickness. This property is called fissility.[1] Shale is the most common sedimentary rock.[2]

Shale
Sedimentary rock
Shale
Composition
Clay minerals and quartz

The term shale is sometimes applied more broadly, as essentially a synonym for mudrock, rather than in the more narrow sense of clay-rich fissile mudrock.[3]