Ans: The pyroxene group of minerals contains minerals that form both in the orthorhombic and monoclinic crystal systems. Orthorhombic pyroxenes are known as orthopyroxenes whereas monoclinic pyroxenes are known as clinopyroxenes. The key feature of all pyroxene structures is the silicon-oxygen tetrahedrons’ linkage by the sharing of two of the four corners to form continuous chains. The chains which extend in an indefinite manner parallel to the crystallographic axis have the composition of (SiO3)n. The SiO3 chains are chained to a given layer of octahedrally coordinated cation bands which in turn extend parallelly to the crystallographic axis. This octahedral layer consists of two unique cation sites.