ANISOTROPY of rocks (from the Greek words "anisos" (not equal) and "tropos" (direction) * EN: anisotropy of rocks; DE: Anisotropie von Gesteinen; FR: anisotropic des roches; ES: anisotropia de las rocas; RU: анизотропия горных пород) is the difference of the values of the properties (deformational, electrical, thermal, magnetic, optical, and others) of the rocks along the different directions.

Anisotropy of minerals and rocks is associated with micro-layering, with ordered orientation of grains and crystals, and with micro-crackedness. Anisotropy of the massifs of the rocks is determined by the orderly bedding of the large structural elements, which are separated by the tectonic ruptures, by the layering, or by the ordered macro-crackedness.

During the conduct of the mining works, during the selection of the methods of destruction, there has the greatest significance the anisotropy of the deformational properties, which is defined as the ratio of the limits of strength (or of the modules of deformation) during the compression and tension of the samples perpendicular and parallel to the bedding. For example, the ratio of the modules of deformation is 1.22 for coal, 1.28 for sandstone, 1.61 for aleurolite.