  If the temperature of the hot thermal plasma in the Early Universe was within
a few orders of magnitude of the Planck scale $M_{\rm Pl}$, then the hoop
conjecture predicts the formation of microscopic black holes from particle
collisions in the plasma. Although these evaporated instantly, they would have
left behind a relic abundance of all stable degrees of freedom which couple to
gravity. Here we show that, upon minimal assumptions of a high reheat
temperature and semiclassical black hole dynamics, this process could have
produced the relic abundance of dark matter observed today for a particle mass
anywhere in the range of $100~\mathrm{keV} \lesssim m_{dm} < M_{\rm Pl}$,
though it could be subdominant to graviton-mediated freeze-in above $m_{dm}
\sim$ MeV. The production mechanism does not rely on any additional assumptions
about non-gravitational dark matter-Standard Model interaction.
