IR and optical spectra have been measured on hydrothermally synthesized pyroxenes with compositions along the joins connccting the compositions CaSiO3, MnSiO3, CaMgSi2O6, CaMnSi2O6, and CaFeSi2O6- The objectives were to compare changes in the spectra with structural changes. The optical spectra are due to ferrous iron and appear insensitive to structural detail. The infrared spectra, particularly the Si-0 stretching vibrations, vary markedly with small structural changes. Each structure type, diopside, wollastonite, bustamite and rhodonite has a distinct ir spectrum. Spectral changes with composition are small. Two phase mixtures can be distinguished. IR evidence indicates that the high-temperature form of hedenbergite has the bustamite rather than the wollastonite structure.