Effects of compositional variation on the crystal structures of pyroxmangite and rhodonite

As adjacent members of pyroxene-pyroxenoid polysomatic series, constructed of fragments of the wollastonite (W) and pyroxene (P) structures, pyroxmangite (WPP) and rhodonite (WP) possess very similar structures with comparable site distortions and cation ordering patterns. The two structures respond quite similarly to cation substitutions; structural responses to cation substitution generally parallel those observed in pyroxenes. Concentrations of strain energy at W-P boundaries likely play a major role in controlling phase transformations in this system.