  We experimentally investigate the nature of 2D phase transitions in a
quasi-2D granular fluid. Using a surface decorated with periodically spaced
dimples we observe interfacial tension between coexisting liquid and crystal
phases. Measurements of the orientational and translational order parameters
and associated susceptibilities indicate that the surface topography alters the
order of the phase transition from a two-step continuous one to a first-order
liquid-crystal one. The interplay of boundary inelasticity and geometry, either
order-promoting or inhibiting, controls the wetting of the granular crystal /
fluid. This order induced wetting has important consequences, determining how
coexisting phases separate spatially.
