Ab initio computer simulations have suggested that pre-melting phenomena occur in the elastic properties of hcp-iron at the conditions of the Earth’s inner core just before melting and that these effects might be responsible for the fact that shear-wave velocities in the inner core determined by seismology are significantly lower than those expected on the basis of computer simulations of the properties of the inner-core constituents. Computer simulations of another hcp metal, Mg, have also indicated that similar pronounced changes in density and in elastic moduli occur (at atmospheric pressure) just prior to melting at, T/Tm > ~ 0.97. The aim of this proposal is to underpin the simulation methodology by investigating experimentally to what extent pre-melting behaviour influences the density and thermal expansion in Mg at atmospheric pressure.