Abstract The elastic properties and the density of ternary glass forming systems within the CaO–SiO 2 –Al 2 O 3 -system (CAS) were evaluated. Different glass compositions near the lowest eutectic (1170 °C) composition within the CaO–Al 2 O 3 –SiO 2 -system have been melted from pure raw materials. Their target compositions differed not more than 4 wt% for each component. Exact chemical compositions were measured by x-ray fluorescence. The density, and acoustic properties were determined and the Young׳s Moduli were derived herefrom. It was of special interest to obtain information on these properties and their dependencies upon small variations in the composition. The density values were between 2.600 and 2.667 g cm −3 and the packing density factors V p of the oxides glasses using the ionic radii of Pauling were in the range from 0.559 to 0.571. The determined data were compared to different model calculations. Density model calculations show relative deviations between 2 and 6%. The values calculated from the model for Young׳s Modulus by Makishima and Mackenzie (1973) [1] were somewhat smaller than the measured ones. The correction by Rocherulle et al. (1989) [3] of the Makishima model showed better agreement with the measured values.