We request two days of beam-time on POLARIS to obtain high resolution measurements of the thermal expansion of dolomite [CaMg(CO3)2]. The experiment forms part of a larger programme in which we are investigating the thermal expansion and elastic properties of polycrystalline geological materials in order to develop predictive thermoelastic models of rocks from the properties of their constituent minerals. Isothermal loading experiments on ENGIN-X and thermal expansion measurements on POLARIS monitoring the build-up of internal strains within dolomite polycrystals during changes in applied load and temperature suggest that elastic twinning may be occurring at low strains. However, in order to interpret these results reliably, we require thermal expansion data for powdered dolomite over a wider temperature range and of a much higher quality than that which is currently available.