The machinability of mica glass-ceramics is evaluated using a tool dynamometer. Several samples with different chemical compositions and microstructures were tested in turning operations using TiCN cermet tools. The cutting rate dependence of specific cutting energy has been studied to find a simple method for the evaluation of machinability, The mechanical strength, the surface roughness of the machined surface and the fracture toughness were measured to support the machining behaviour. For the determination of machinability, the specific cutting energy at low cutting rate conditions, neglecting an elastic impact effect, and the slope of the log-log plot of the specific cutting energy versus cutting rate were considered as the reasonable parameters. These results are correlated with the microstructure and the hardness of the workpiece. In particular, the microhardness of the sample is shown to control the cutting characteristic.