  We evaluate the percolation threshold values for a realistic model of
continuum segregated systems, where random spherical inclusions forbid the
percolating objects, modellized by hard-core spherical particles surrounded by
penetrable shells, to occupy large regions inside the composite. We find that
the percolation threshold is generally a non-monotonous function of
segregation, and that an optimal (i. e., minimum) critical concentration exists
well before maximum segregation is reached. We interpret this feature as
originating from a competition between reduced available volume effects and
enhanced concentrations needed to ensure percolation in the highly segregated
regime. The relevance with existing segregated materials is discussed.
