Abstract:
An intrinsic property of polycrystalline materials is the orientation distribution of crystallites. In some cases this distribution is random, yet often there is preferred orientation of crystallites relative to macroscopic axes that may have been attained during a deformation process. Many rocks—metamorphic, igneous as well as sedimentary—display non-random orientation distributions that are the cause for anisotropy of macroscopic physical properties. Interpretation of textures in materials has to rely on a quantitative description of orientation characteristics. Two types of preferred orientations need to be distinguished: The shape preferred orientation (or often abbreviated SPO) describes the orientation of grains with anisotropic shape. The lattice preferred orientation (LPO) or “texture” refers to the orientation of the crystal lattice. (LPO is an unfortunate term since the lattice does not always uniquely describe the crystal orientation, as in the trigonal mineral quartz with a hexagonal unit cell.
