Ceramics from the magnesia-alumina-silica (MAS) system are common products of the ceramic industry. The phase composition of these systems can be rather complex, especially when feldspar is added as a flux, and thus attempts to correlate the composition and structure of these ceramics to their properties are quite rare, especially when considerable amounts of glass phase and sapphirine appear after firing. In this paper an attempt is made to correlate, for a talc-kaolin-alumina-feldspar mixture resulting in cordierite-sapphirine ceramics after firing to 1250 °C, the resulting elastic properties (Young’s modulus), as determined via the impulse excitation technique (IET), with the phase composition, determined via X-ray diffraction (XRD). Moreover, it is shown how the evolution of the phase composition and microstructure is reflected in the temperature dependence of Young’s modulus and damping during heating-cooling cycles with maximum temperatures ranging from 1000 to 1250 °C.