Meteorite MIL03346, recovered from Antarctica, is a nakhlite: an augite clinopyroxenite inferred to have originated from Mars' surface. MIL03346 contains ~70% augite and 3% olivine in a fine-grained mesostasis of basaltic glass, olivine, titanomagnetite, and pyrrhotite. Part of the olivine is altered to fine-grained ferric clays and oxides -- "iddingsite" as described in other nakhlites. Chemical compositions of augite and olivine (FeO/MnO and Fe/Mg) are nearly identical to those of other nakhlites, and are consistent with a Martian origin. The augite contains significant Fe³⁺: ~24% of total iron by Mössbauer spectroscopy, and ~13% by elemental analyses and crystal chemistry. The proportion of Fe³⁺ in augite is consistent with high-temperature equilibration near the QFM oxygen buffer. Thermal emission spectra are similar to those of other nakhlites. Visible to mid-IR spectra of MIL03346 show the same absorption features as do other nakhlites, but at distinctly lower reflectances (which likely represent Fe³⁺ in augite and magnetite). MIL03346 appears to contain the most Fe³⁺ of any Martian meteorite studied to date, and to have come from the most oxidizing magmatic environment yet reported.