  In the framework of schematic hard spheres lattice models we discuss Edwards'
Statistical Mechanics approach to granular media. As this approach appears to
hold here to a very good approximation, by analytical calculations of Edwards'
partition function at a mean field level we derive the system phase diagram and
show that ``jamming'' corresponds to a phase transition from a ``fluid'' to a
``glassy'' phase, observed when crystallization is avoided. The nature of such
a ``glassy'' phase turns out to be the same found in mean field models for
glass formers. In the same context, we also briefly discuss mixing/segregation
phenomena of binary mixtures: the presence of fluid-crystal phase transitions
drives segregation as a form of phase separation and, within a given phase,
gravity can also induce a kind of ``vertical'' segregation, usually not
associated to phase transitions.
