We present three reasons for the formation of gravitational bound states of primordial black holes, called holeums, in the early universe. Using Newtonian Gravity and nonrelativistic quantum mechanics we find a purely quantum mechanical mass-dependent exclusion property for the nonoverlap of the constituent black holes in a holeum. This ensures that the holeum occupies space just like ordinary matter. A holeum emits only gravitational radiation whose spectrum is an exact analogue of that of a hydrogen atom.A part of this spectrum lies in the region accessible to the detectors being built. The holeums would form haloes around the galaxies and would be an important component of the dark matter in the universe today. They may also be the constituents of the invisible domain walls in the universe.---