Cold sintering of cobalt powder (up to 1.2 GPa) was accompanied by measurements of density and thermal diffusivity. Dependence of density change upon pressing pressure is derived. Thermal diffusivity of the material was measured using photoacoustic two-beam phase-lag single frequency method. A formula is presented for the thermal conductivity of porous granular materials on the basis of the effective medium theory. Experimental results and effective medium theory were correlated and the obtained results compared with the literature data.