All non-random crystallographic orientations in a crystal or in a rock are termed as "preferred orientations" or texture. A large amount of rocks display preferred orientations of crystallites and these alignments deeply influence the anisotropy of physical properties. As a rule, preferred orientations occur during re-crystallization or phase transformation and can be recognized both in the lattice of the single crystal (Lattice Preferred Orientation) and in the whole rock - the last, frequently called "fabric anisotropies".
In clay-rich rocks, fabric anisotropies are the consequence of the strain path and/or deposition mechanisms related to several microscopic features typical of clay minerals as phyllosilicates. In fact, significant literature data designate crystal chemical and crystal physics properties of phyllosilicates as fundamental factors for the formation of preferential orientations not only in low-grade metamorphic rocks, but also in shales and deformed mudstones. A qualitative and quantitative understanding of the orientations' distribution in these rocks can support reconstruction of geological events but also tectonic studies and, more recently, geotechnics and landslides monitoring and prevention.
In the light of previous considerations, the session aims to contributions concerning: i) strain and texture measurements on geological (clay-sized) samples; ii) measurements of lattice preferred orientations in phyllosilicate single crystals such as micas, chlorites etc; iii) applications of deformation measurements via texture analysis in geotechnics and landslides control; iv) novel experimental methodologies as well as data interpretation software for texture measurement and analysis.