Crystal system

A crystal system is a class of point groups (a group of geometric symmetries that keep at least one point fixed). A study of the set of symmetry elements of mineral specimens showed that they can be grouped into 7 crystal systems (cubic, tetragonal, hexagonal, rhombohedral, orthorhombic, monoclinic and triclinic), each defined by a fundamental polyhedron representing the simplest possible form possessing all the symmetry elements of the system.