  It has recently been pointed out that if the surface tension of quark matter
is low enough, the surface of a strange star will be a crust consisting of a
crystal of charged strangelets in a neutralizing background of electrons. This
affects the behavior of the surface, and must be taken into account in efforts
to observationally rule out strange stars. We calculate the thickness of this
``mixed phase'' crust, taking into account the effects of surface tension and
Debye screening of electric charge. Our calculation uses a generic
parametrization of the equation of state of quark matter. For a reasonable
range of quark matter equations of state, and surface tension of order a few
MeV/fm^2, we find that the preferred crystal structure always involves
spherical strangelets, not rods or slabs of quark matter. We find that for a
star of radius 10 km and mass 1.5 Msolar, the strangelet-crystal crust can be
from zero to hundreds of meters thick, the thickness being greater when the
strange quark is heavier, and the surface tension is smaller. For smaller quark
stars the crust will be even thicker.
