  Assuming a population of Black Holes (BHs) with masses in the range inferred
by LIGO/Virgo from BH mergers, we use quasar microlensing observations to
estimate their abundances. We consider a mixed population of stars and BHs and
the presence of a smooth dark matter component. We adopt reverberation mapping
estimates of the quasar size. According to a Bayesian analysis of the measured
microlensing magnifications, a population of BHs with masses $\sim$
30$M_{\odot}$ constitutes less than 0.4 % of the total matter at 68 %
confidence level (less than 0.9 % at 90 % confidence). We have explored the
whole mass range of LIGO/Virgo BHs finding that this upper limit ranges from
0.5 % to 0.4 % at 68 % C.L. (from 1.1 % to 0.9 % at 90 % C.L.) when the BHs
mass change from 10 to 60$M_{\odot}$. We estimate a 16 % contribution from the
stars, in agreement with previous studies based on a single mass population
that do not consider explicitly the presence of BHs. These results are
consistent with the estimates of BH abundances from the statistics of
LIGO/Virgo mergers and rule out that PBHs (or any type of compact objects), in
this mass range constitute a significant fraction of the dark matter.
