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Electron transport properties of single crystal and polycrystalline natural mineral galena (PbS) samples from the Trepča mine, Yugoslavia, were determined using the photoacoustic frequency transmission technique. Their thermal diffusivity (D_T ≈ 0.16 × 10^-5 m² s^-1), the coefficient of diffusion (D between 0.15 × 10^-2 0.16 × 10^-2 m² s^-1) and lifetime of the excess carrier (τ ≈ 35 μs and the front and rear recombination velocity (S_g ≈ 65.5 m s^-1 and S_b ≈ 66.4 m s^-1, respectively), were calculated by comparing the experimental results and the theoretical photoacoustic amplitude and phase signals. The lattice parameter obtained by X-ray work was a = 5.936 Å. The free carrier concentration of these single-crystal samples was measured using the Hall method (N = 3 × 10¹⁸ cm^-3). Measurements of the optical reflectivity of the same samples, as a function of wavelength, in the infrared and far infrared ranges, were performed. In the far infrared range a free electron plasma frequency was observed and numerically analyzed, using the least-squares fitting procedure. The values of optical parameters were calculated and the value of the free carrier concentration obtained by the Hall method was confirmed.