  An effective, low-energy, field theory of s-wave quarkonia, constituent heavy
quarks, and gluons is constructed which is manifestly gauge invariant. The
interaction Lagrangian has the form of a twist expansion, as typically
encountered in hard processes, and involves derivatives of arbitrary order. The
parameters in the interaction are related with the non-relativistic wave
function, and standard results for $Q\bar{Q}$ inclusive decays and radiative
transitions are shown to be easily recovered. The light-cone gluon momentum
distribution at very small $x$ is calculated and shown to be uniquely
determined by the non-relativistic wave function. The distribution has a part
which goes as $x^{-1}logx$, ie. is more singular than the usually assumed $1/x$
behaviour. The fragmentation function for a virtual gluon to inclusively decay
into an $\eta_c$ or $\eta_b$ is also calculated. We find that the emission of
low momentum gluons makes this process quite sensitive to assumptions about the
binding of heavy quarks in quarkonia.
