A simple method of analysing the results of deformation experiments on synthetic two-phase aggregates is presented and applied to some tests on calcite-halite aggregates. The approach involves replacing the observed mechanical behaviour of real two-phase materials of coarse microstructure, with a phase volume fraction weighted mechanically equivalent representation in which each phase is assigned its own single-valued stress and its own single-valued strain. Such a representation can be solved for the stresses and strains in the two phases and the results compared with the stresses and strains as determined from the deformation microstructures. In principle, it is then possible to constrain which of the features of the microstructure are mechanically significant. The stresses supported by the synthetic calcite-halite aggregates suggest a strong partitioning of the deformation into the halite at all volume fractions of calcite, and yet analysis of the halite strains from the deformation microstructures indicates that there is little or no strain partitioning between the phases. However, these conflicting results may be reconciled by using the calcite contiguous volume, rather than the actual calcite volume fraction, to characterize the strength of the aggregates with respect to those of their component phases. © 1993.