Pyroxenes: a group of inosilicates that crystallize in the Orthorhombic, Monoclinic, and Triclinic Systems. This group includes important gem materials such as Diopside, Enstatite, Jadeite, and Spodumene. Pyroxenes are composed of isomorphic mixtures of divalent metals (Ca, Mg, Fe, Mn) and, in part, trivalent elements (Al, Fe, Cr), sometimes with alkali metals (Na, Li). Their structure is based on single chains of SiO₄ tetrahedra. Silicon is at the center of the tetrahedron, whose four Oxygen atoms are linked at two vertices to form infinite chains, resulting in an overall SiO₃ ratio. These chains develop parallel to the “C” axis.
