  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-dependant 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.
