A model based on Rayleigh-Gans-Debye light scattering theory has been developed to describe the light transmission properties of fine-grained, fully dense polycrystalline ceramics consisting of birefringent crystals. This model extends light transmission models based on geometrical optics, which are only valid for coarse-grained microstructures, to smaller crystal sizes. We verify our model by measuringthe light transmission properties of fully dense (>99.99%) polycrystalline alpha-alumina (PCA) with mean crystal sizes ranging from 60 mm down to 0.3 mm. The remarkable transparency exhibited by PCA samples with small crystal sizes (< 2 mm) is very well explained by thismodel.