Wereport resonant inelastic x-ray scattering (RIXS) excited by circularly polarizedx rays on Mn-Zn ferrite at the Mn L_2,3 resonances.We demonstrate that crystal-field excitations, as expected for localized systems,dominate the RIXS spectra and thus their dichroic asymmetry cannotbe interpreted in terms of spin-resolved partial density of states,which has been the standard approach for RIXS dichroism. Weobserve large dichroic RIXS at the L₂ resonance which weattribute to the absence of metallic core hole screening inthe insulating Mn ferrite. On the other hand, reduced L₃-RIXSdichroism is interpreted as an effect of longer scattering timethat enables spin-lattice core hole relaxation via magnons and phononsoccurring on a femtosecond time scale.