Sphericity (geology)

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In geology, sphericity is a measure of how spherical a body is.


The term sphericity was defined in 1935 by the geologist Hakon Wadell. The sphericity of a body K is the ratio of the surface area of ​​a sphere of equal volume to the surface area of ​​the body:


where denotes the volume of the body and its surface area.


In sedimentology and soil micromorphology , sphericity is used as an approximation for the grain shape . Since a calculation would be too time-consuming, it is usually estimated using comparison tables , which also enable the grain rounding to be determined. The sphericity is then not given as a numerical value, but by classification (e.g. prismoidal , subprismoidal, spherical , subdiscoidal, discoid ).

Sphericity of known bodies

Surname image volume surface Sphericity
Platonic solids
Tetrahedron Tetrahedron
Cube (hexahedron) Hexahedron (cube)

octahedron Octahedron

Dodecahedron Dodecahedron

Icosahedron Icosahedron
Bodies with nonplanar faces
ideal cone


ideal cylinder

ideal torus


Web links


  1. Hakon Wadell: Volume, Shape and Roundness of Quartz Particles . In: Journal of Geology . 43, 1935, pp. 250-280.