“…Wide chemical substitutions may occur within each site: Ca, Mg, Fe, Na, Mn, Ni, Li, Zn, Mg, and Fe 2+ for M2, Mg, Fe 2+ , Fe 3+ , Ti, In, Sc, Al, Ga, Mn, Co, Ni, Zn for M1, and Si, Al, and Ge for T . Therefore, pyroxenes are well suited to test the effect of chemical substitution in a relatively simple structure: the extent and the effect of changes in cation radii, site occupancy, and crystal field stabilization can be experimentally monitored …”