(adj.) Geophysics, Geology, Shale Gas. Having directionally dependent properties. For a crystal of a mineral, variation in physical properties observed in different directions is anisotropy. In rocks, variation in seismic velocity measured parallel or perpendicular to bedding surfaces is a form of anisotropy. Often found where platy minerals such as micas and clays align parallel to depositional bedding as sediments are compacted, anisotropy is common in shales. Ant: Isotropic. See: Aeolotropy, Anisotropic Formation, Anisotropy, Birefringence, Extensive Dilatancy Anisotropy, Heterogeneous Formation, Raypath, Seismic Velocity, Velocity