Shale is clastic sedimentary rock composed Clastic Sedimentary Rock composed of clay and silt with clay domination with fissile texture fissility properties.
The major difference from muddstone is that it has fissility properties.
See also
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Petroleum Industry / Upstream / Subsurface E&P Disciplines / Petroleum Geology + Petrophysics / Rock / Sedimentary Rock / Clastic Sedimentary Rock
[ Muddstone ]
[ Petrophysics / Volumetric Rock Model / Shaliness (Vsh) ]