The elastic, piezoelectric and dielectric properties of proustite (Ag 3AsS3) and pyrargyrite (Ag3SbS3) and their first-order temperature coefficients have been determined at room temperature. A full set of the relevant coefficients has been derived for proustite and these have been used for the prediction of the material's SAW properties as a function of temperature. A more limited set of coefficients has been derived for pyrargyrite and these are compared with the coefficients for proustite. Both materials show markedly anomalous elastic constant behaviour as a function of temperature and have properties which appear to be promising for low velocity SAW applications.