Dissolution rate of gypsum irregular particles in four non-Newtonian liquids at low Reynolds numbers (creeping flow regime) has been compared with the predictions of the available correlations based on the power law model for mass transfer in fixed bed. The flow behaviour index has been varied from 0.976 to 0.271. The shape coefficient and the coefficient of surface availability experimentally determined have been used as an attempt to reduce the problem to mass transfer from spheres. A new method for evaluation of the diffusivity of gypsum in the liquids have been applied. It has been shown that the empirical correlations based on the capillary model need to be complemented by the Pigford's delta factor as to describe the mass transfer at very different flow behaviour index by a single equation.