  A simulated annealing algorithm is applied to the reconstruction of
two-dimensional porous media with prescribed correlation functions. The
experimental correlation function of an isotropic sample of Fontainebleau
sandstone and a synthetic correlation function with damped oscillations are
used in the reconstructions. To reduce the numerical effort we follow a
proposal suggesting to evaluate the correlation functions only along certain
directions. The results show, that this simplification yields significantly
different micro-structures as compared to a full evaluation of the correlation
function. In particular we find that the simplified reconstruction method
introduces an artificial anisotropy that is originally not present.
