  We are interested here in a birth-and-growth process where germs are born
according to a Poisson point process with invariant under translation in space
intensity measure. The germs can be born in free space and then start growing
until occupying the available space. In order to consider various way of
growing, we describe the crystals at each time through their geometrical
properties. In this general framework, the crystallization process can be
caracterized by the random field giving for a point in the space state the
first time this point is reached by a crystal. We prove under general
conditions that this random field is mixing in the sens of ergodic theory and
obtain estimates for the coefficient of absolute regularity.
