Abstract
Infrared transmission spectra of alpha -Fe2O3 microcrystals much smaller than the wavelength of incident light were measured over a wide range of dielectric constant of the surrounding medium. Features specific to the surface mode absorption were found. Detailed analysis of the observed spectra was made on the basis of the generalised theory of the average dielectric function. It is shown that the observed spectra can be well explained by taking into account the optical anisotropy, the particle shape and the broadening mechanisms.