In the present paper, we test the suitability of a previously proposed model by Gao et al.(9) for describing the hardness of more complicated, multicomponent crystals by both calculating and measuring the hardness of a diopside crystal. We analyze the limitations of the model and suggest that factors like load and temperature should be considered in the model. The calculated value of hardness of the diopside crystal is compared with the Vickers hardness values measured at different loads. A good agreement is found between the calculated hardness and the value measured at 25 degrees C at a load of 0.5 N. Crystal orientation and measurement temperature have an impact on the experimental value of hardness of the crystals.