The adiabatic elastic properties of two synthetic polycrystalline garnets, with an average grain size of 0.8 micron, and with compositions of 67% pyrope-33% majorite and 66% majorite-34% pyrope, have been measured at ambient conditions by Brillouin spectroscopy. Within the experimental uncertainties the measured bulk and shear moduli of the two majorites are comparable to those of pyrope. The dissolution of pyroxene in the garnet structure therefe, does not significantly affect the elastic properties in the pyrope-majorite solid solution series. ¿American Geophysical Union 1990