The acoustic emission (AE) and fractoluminescence (FL) techniques were applied to study the impact damage in sintered powders of SiO2, SiC and Al2O3 and their single crystal counterparts. The measured AE intensities and FL amplitudes are proportional to the energy release in events of microcrack nucleation and chemical bond breakage, respectively. In crystals, the AE method showed the random energy release in crystals, and the scaling energy distributions in powders. The FL method evidenced the self-similar energy distributions in α-SiO2 and α-SiC due to nanostructural heterogeneity inherent even to homogeneous solids, while luminescence from α-Al2O3 was specific for the random process.