Mixed modifier glasses can be looked as being mixtures of the corresponding single modifier matrices. Static properties of mixed modifier glasses can be described by using the parameters of the constituting matrices. Density, molar volume, refractive index, molar refraction and linear thermal expansion coefficient of various types of mixed modifier glasses depend on the molar fraction and parameters of the forming matrices. The fraction of four-coordinated boron atoms in mixed modifier borate glasses can be treated in a similar manner.