Diopside-kosmochlor solid solutions have been synthesized at 1 atm and 15Kb and their crystal field spectra have been measured. Solubility is very much increased with pressure and there is only a narrow immiscibility field. The limits of solubility at 1100°C and 15Kb were found to be 19.5 wt percent of kosmochlor molecule in diopside and about 55 wt percent of diopside molecule in kosmochlor, respectively. Crystal field splitting parameter 10Dq and Racah parameter B are nearly constant throughout this solid solution series as expected from their structural analysis.