Tavares and King [Tavares, L.M., and King, R.P., A Useful Model for the Calculation of the Performance of Batch and Continuous Jigs, Coal Preparation, 15, 99-128, 1995.] have proposed an elegant equilibrium stratification model for stratification of feed particles in gravity concentrators namely, the pinched sluice, the Reichert cone and the jig to account for particle segregation in the bed in order to aid particle separation. The model considers feed distributed in particle density but strictly of monosize particles to evaluate partition coefficients of separation, product distributions in terms of particle density as well as mass yield of solids at various cut heights of the stratified bed for both batch and continuous operations. This paper extends this model to incorporate the particle size effects along with particle density effects, by considering a bivariate feed distribution that gets stratified in the operating unit. It is shown by the simulation studies that the bivariate partition functions obtained numerically at various bed cut heights from the stratification model are qualitatively matching to the nature of partition surfaces normally found in literature for gravity concentrators. (C) 2007 Elsevier B.V. All rights reserved.