  We study spectral properties of Schr\"odinger operators on $\RR^d$. The
electromagnetic potential is assumed to be determined locally by a colouring of
the lattice points in $\ZZ^d$, with the property that frequencies of finite
patterns are well defined. We prove that the integrated density of states
(spectral distribution function) is approximated by its finite volume
analogues, i.e.the normalised eigenvalue counting functions. The convergence
holds in the space $L^p(I)$ where $I$ is any finite energy interval and $1\leq
p< \infty$ is arbitrary.
