Results of determination of the refractive index of 79 glass samples by the thermo-immersion method using the GRIM2 system are presented in the current work. They originated from three use-type groups, i.e. building windows, car windows and car headlamps. Observed differences in values of refractive indices between the analysed glass samples, originating from the same group and also from different groups, are small and the application of statistical methods allowed us to differentiate samples on the basis of determined refractive index values.