  Do white dwarfs have inner cores made of iron? Neutron rich nuclei like
$^{56}$Fe experience a net gravitational force and sediment toward the core.
Using new phase diagrams and molecular dynamics simulations, we show that
$^{56}$Fe should separate into mesoscopic Fe-rich crystallites due to its large
charge relative to the background. At solar abundances, these crystallites
rapidly precipitate and form an inner core of order 100 km and $10^{-3}
M_\odot$ that may be detectable with asteroseismology. Associated cooling
delays could be up to a Gyr for low mass white dwarfs but are only $\sim$0.1
Gyr for massive white dwarfs, so while this mechanism may contribute to the
Q-branch the heating is insufficient to fully explain it.
