  We introduce a one-dimensional sandpile model with $N$ different particle
types and an infinitesimal driving rate. The parameters for the model are the
N^2 critical slopes for one type of particle on top of another. The model is
trivial when N=1, but for N=2 we observe four broad classes of sandpile
structure in different regions of the parameter space. We describe and explain
the behaviour of each of these classes, giving quantitative analysis wherever
possible. The behaviour of sandpiles with N>2 essentially consists of
combinations of these four classes. We investigate the model's robustness and
highlight the key areas that any experiment designed to reproduce these results
should focus on.
