The glasses belonging to the CaO-MgO-Al2O3-SiO2 quaternary system are materials largely used in industrial applications by virtue of their melting and devitrifible properties. A systematic study of several compositions falling in the anorthite (CaO-Al(2)O(3)2SiO(2))-diopside (CaO-MgO-2SiO(2)) system has been carried out by means of thermal and physical measurements in order to obtain the relationships between the structure and the properties of the glasses. The experimental evidence has been compared to molecular dynamic simulation results. Attention has been devoted to the definition of the structural role in the glass formulation played by Al3+ and Mg2+ which can behave as network formers or modifiers depending on their coordination number in the structure.