Magnetite a natural iron oxide (Fe3O4) was used to examine its influence on rubber compounds. Compounds based on NR and EPDM where easily processable, with limited influence of the filler on viscosity and vulcanisation time. Densities of 3 g/cm(3) were reached, while mechanical properties of the compounds were still good, even after ageing the samples. The effect of magnetite on thermal and electrical conductivity was analysed, showing an increase in both. Furthermore the magnetic properties were measured, showing that the compounds became ferrimagnetic upon adding magnetite. The microwave heatability of the compounds was characterised, showing an increased heat-up rate when magnetite was present in the compounds. The study showed that the unique mix of properties of magnetite can be easily incorporated in rubber-compounds.