  We study in this work the dynamics of a collection of identical hollow
spheres (ping-pong balls) that rest on a horizontal metallic grid. Fluidization
is achieved by means of a turbulent air current coming from below. The upflow
is adjusted so that the particles do not levitate over the grid, resulting in
quasi-two-dimensional dynamics. We show that the behavior of diffusion and
correlations in this system is particularly rich. Noticeably as well (and
related to the complex dynamical behavior), a variety of phases appear, with
important peculiarities with respect to analogous setups. We observe gas,
liquid, glass, and hexagonal crystal phases. Most notably, we show that the
melting of the hexagonal crystal occurs in coexistence with a liquid phase.
This strikingly differs from the corresponding transition in a purely
two-dimensional systems of air-fluidized disks, for which no phase coexistence
has been reported in the literature.
