  We present a purely gravitational infra-red-calculable production mechanism
for dark matter (DM). The source of both the DM relic abundance and the hot
Standard Model (SM) plasma is a primordial density of micro black holes (BHs),
which evaporate via Hawking emission into both the dark and SM sectors. The
mechanism has four qualitatively different regimes depending upon whether the
BH evaporation is `fast' or `slow' relative to the initial Hubble rate, and
whether the mass of the DM particle is `light' or `heavy' compared to the
initial BH temperature. For each of these regimes we calculate the DM yield,
$Y$, as a function of the initial state and DM mass and spin. In the `slow'
regime $Y$ depends on only the initial BH mass over a wide range of initial
conditions, including scenarios where the BHs are a small fraction of the
initial energy density. The DM is produced with a highly non-thermal energy
spectrum, leading in the `light' DM mass regime ($\sim260\,\mathrm{eV}$ and
above depending on DM spin) to a strong constraint from free-streaming, but
also possible observational signatures in structure formation in the spin 3/2
and 2 cases. The `heavy' regime ($\sim1.2\times 10^8\,\mathrm{GeV}$ to
$M_{\mathrm{Pl}}$ depending on spin) is free of these constraints and provides
new possibilities for DM detection. In all cases there is a dark radiation
component predicted.
