  By detailed Molecular Dynamics and Monte Carlo simulations %of a realistic
model we show that granular materials at rest can be described as
thermodynamics systems. First we show that granular packs can be characterized
by few parameters, as much as fluids or solids. Then, in a second independent
step, we demonstrate that these states can be described in terms of equilibrium
distributions which coincide with the Statistical Mechanics of powders first
proposed by Edwards. We also derive the system equation of state as a function
of the ``configurational temperature'', its new intensive thermodynamic
parameter.
