Nanoindentation has revealed significant scatter of the microscale hardness and elastic modulus of an amorphous SiCN ceramic, because of structural inhomogeneities (nanopores and clusters of free carbon within the material). As a consequence of the common feature, an amorphous nature, SiCN, in regard to its mechanical properties, resembles SiO2 glass more than SiC or Si3N4, However, because of the stronger Si-C and Si-N covalent bonding, SIGN is harder and stiffer than SiO2. The mean hardness-13 +/- 2 GPa, measured at a load of 250 mN for SiCN-is approximately half that of polycrystalline Si3N4 (24.9 +/-0.6 GPa) but higher than that of SiO2 glass (8.9 +/- 0.04 GPa), The elastic modulus of the SiCN, measured at a load of 250 mN, is 121 +/-10 GPa.