The radiative properties of hematite (alpha-Fe2O3) samples of different particle size distributions obtained by the pressure welding procedure were investigated. Measurements were made in the ultraviolet and visible spectra, and the radiative properties of samples were assessed using the discrete dipole approximation (DDA) in the visible spectrum. The accuracy of DDA was evaluated against the Mie theory results in terms of the optical efficiency in the short and long wavelength range of 0.20-50 mu m. The coating on particles due to the aging effect was examined using scanning electron microscopy (SEM) images. The measured absorbance values of the samples displayed significant differences in the wavelength range of 0.20-0.50 mu m. Among the measured absorbance of three samples with sizes of 37 mu m, 63 mu m, and 125 mu m, the most prominent change in absorbance was observed in the sample consisting of the smallest diameter, while the sample containing the largest size had the highest absorbance values in the spectral range. The change with oscillation in wavelength of the absorbance was also observed in the DDA results. Both the experimental and calculated results presented in this study indicate that the absorption behaviour of hematite particles depends on the particle size, wavelength and production process.