The Carman-Kozeny correlation is applied to a medium which is consolidated, highly porous and anisotropic: the expanded then compressed natural graphite. The effective textural properties (i.e. the mean pore diameter, porosity and tortuosity) have been measured by a mercury porosimeter and a heterogeneous diffusion cell. The texture and the permeability (according to the Darcy's law) measured for the two main directions of these orthotropic porous media change over a very wide range depending on their apparent mass densities. Experimental data show that only a part of the total porosity participates in the gas flow in steady state conditions.