Using spherical and oblate spheroidal particles, we investigated the influence of the shape of the dust aerosol on the imaginary part of the refractive index n_i obtained from the photometric observations carried out during the highest activity period in the global dust storm in 1971. A similar analysis for high transparency periods was performed relative to the estimates of the mean particle radius r₀ and the optical thickness of the dust layer τ₀ which were obtained from polarimetric measurements. The adopted shape of aerosol was found to affect these optical parameters. Namely, the values of n_i, r₀, and τ₀ obtained for spheroidal particles proved to be approximately a factor of 2 greater than those for spheres. Anyway, they remain to be much lower than the estimates found for these parameters from space experiments. So far, the origin of such a discrepancy is not clear.