Equantcy versus sphericity

ABSTRACT The shape of a particle is commonly characterized by its sphericity. In geology, sphericity is determined by comparing a grain's length, width and breadth diameters. This type of measurement does not indicate how close the particle is to a true spherical shape, and cubes, tetrahedrons, and true spheres all have the same degree of sphericity. Because the term sphericity is misleading, implying that its determination takes roundness into account, a different term should be used. I propose that whenever the shape of a grain is determined by measuring or estimating the lengths of its main axes, we regard this as determining its degree of equantcy.