A recent paper [Bouhifd et al., 1996> has given the measured thermal expansivity, &agr;, of forsterite up to 1900 K, which is 2.5 times the Debye temperature, &THgr;. Using the measured &agr;, Bouhifd et al. [1996> found that the &agr;KT curve (where KT is the isothermal bulk modulus) is parallel to the T axis, showing that (∂(&agr;KT)/∂T)p=0. Using these results, I show that (∂CV/∂T)p>0 at high T, requiring CV to be anharmonic, is in agreement with other recent work. Further, I show that Bouhifd et al.'s [1996> work requires that all vestiges of anharmonicity be absent in the thermal pressure and the thermal expansivity of forsterite. Thus it is proven that forsterite is a solid that is both anharmonic in CV and quasiharmonic in the thermal pressure in the high-temperature region. ¿ American Geophysical Union 1996