A thermoelectric module TM based on natural pyrite has been designed and built up. It is formed by 12 couples of n- and p-type blocks of pyrite from Spain and Germany mines, respectively. Previously, a detailed study of transport properties of different provenances pyrites has been carried out, in order to select adequate specimens. N-type pyrite from Spain with Seebeck coefficient (S)of ~ -600 µV/K and electrical resistivity (r) of ~ 0.24W.cm is used. As p-type pyrite, natural pieces from Germany with S ~ 370µV/K and r ~ 8 W.cm, was chosen. The internal resistance of this device was around 700W, the electric power produced was of about microwatts and the TM efficiency was 2.10-3 %.