  We demonstrate low-excitation transport and separation of two-ion crystals
consisting of one beryllium and one calcium ion, with a high mass ratio of
$4.4$. The full separation involves transport of the mixed-species chain,
splitting each ion into separate potential wells, and then transport of each
ion prior to detection. We find the high mass ratio makes the protocol
sensitive to mode crossings between axial and radial modes, as well as to
uncontrolled radial electric fields that induce mass-dependent twists of the
ion chain. By controlling these stages, we achieve excitation as low as
$\bar{n}=1.40 \pm 0.08$ phonons for the calcium ion and $\bar{n}=1.44 \pm 0.09$
phonons for the beryllium ion. Separation and transport of mixed-species chains
are key elements of the QCCD architecture, and may also be applicable to
quantum-logic-based spectroscopy of exotic species.
