  We present the full phase diagram of the dumbbell model of spin ice as a
function of temperature, chemical potential and staggered chemical potential
which breaks the translational lattice symmetry in favour of charge crystal
ordering. We observe a double winged structure with five possible phases,
monopole fluid (spin ice), fragmented single monopole crystal phases and double
monopole crystal, the zinc blend structure. Our model provides a skeleton for
liquid-liquid phase transitions and for the winged structures observed for
itinerant magnets under pressure and external field. We relate our results to
recent experiments on Ho$_2$Ir$_2$O$_7$ and propose a wide ranging set of new
experiments that exploit the phase diagram, including high pressure protocols,
dynamical scaling of Kibble-Zurek form and universal violations of the
fluctuation-dissipation theorem.
