Mica is an extensive group of minerals characterized by perfect {001} cleavage, i.e. the ability to easily split into very thin sheets with a flat surface parallel to the face of the third pinacoid. Muscovite and phlogopite have the most important industrial value. Mica have high electrical characteristics, incombustibility and great mechanical strength, they are also thermally and chemically stable, and are not very hygroscopic. Mica crystallize in a monoclinic system, approaching hexagonal . forms. Under the influence of mechanical effects mica deform, lose their properties and become unsuitable for industrial purposes, so, of course, the study of deformed mica is paid much attention.