  It has been recently suggested that small mass black holes (BHs) may become
unstable due to quantum-gravitational effects and eventually decay, producing
radiation, on a timescale shorter than the Hawking evaporation time. We argue
that the existence of a population of low-mass Primordial Black Holes (PBHs)
acting as a fraction of the Universe dark matter component can be used to test
proposed models of quantum decay of BHs via their effect on galaxy number
counts. We study what constraints future galaxy clustering measurements can set
on quantum-gravity parameters governing the BH lifetime and PBH abundance. In
case of no detection of such effects, this would rule out either the existence
of a non-negligible number of small PBHs, or the BH quantum decay scenario (or
both). In case of independent observations of PBHs, the observables discussed
here could be used to study the quantum effects that modify the final fate of
BHs.
