The observables of supergravity are defined to be the phase space gauge invariant objects of the theory. Dirac eigenvalues are obsevables of Euclidean gravity on a compact manifold [1,2,3]. We resume the basic results for super-gravity [4,5], [6,7]. The general setting which we consider is of minimal supergravity in four dimensions on a compact spin manifold without boundary endowed with an Euc...