  We present the results of an experimental study of patterned segregation in a
horizontally shaken shallow layer of a binary mixture of dry particles. As the
compacity, $C$, of the mixture was increased, the evolution of three distinct
phases was observed. We classify them as binary gas, segregation liquid and
segregation crystal phases using macroscopic and microscopic measures. The
binary gas to segregation liquid transition is consistent with a continuous
phase transition and includes the characteristic feature of critical slowing
down. At high compacities we observed an intriguing slow oscillatory state.
