A new mathematical model for the description of segregation and dispersion in jigging beds is proposed. The model relies on the dynamic simulation of the porosity distribution in the bed. It considers the influence of the main operational variables of a jig, and includes these variables as direct inputs. By combining a phenomenological model with a DEM model, it makes use of a limited number of discrete elements, which is not possible in conventional DEM codes. The model has been fitted to experimental data resulting from a series of batch jigging tests performed at different conditions. It was found that the model describes with good accuracy the experimental data. The model also gives important insights into the jigging mechanism, in particular, into the relationship between the expansion of the bed and the rate of stratification. (C) 2015 Elsevier Ltd. All rights reserved.