Northwest Africa 2626

Northwest Africa

Purchased 2004 November

Martian meteorite (basaltic shergottite)

A 31.07 g completely crusted stone was purchased by MFarmer.  Classification and mineralogy (J. Wittke and T. Bunch, NAU; A. Irving and S. Kuehner, UWS): olivine-orthopyroxene-phyric basaltic rock composed of euhedral to subhedral olivine phenocrysts and preferentially-oriented, prismatic low-Ca pyroxene phenocrysts in a groundmass of zoned pigeonite (Fs_26.4Wo_12.4 to Fs_34.1Wo_12.4) FeO/MnO = 27-31; maskelynite (An_66.0-71.0Or_0.4), olivine (Fa_43.6-47.3) FeO/MnO = 51-58; Ti-chromite (Cr/(Cr+Al) = 0.72-0.79; 9.2-19.8 wt. % TiO₂), chromite (Cr/(Cr+Al) = 0.71-0.86; 0.7-2.0 wt. % TiO₂), merrillite, ilmenite, ulvöspinel and pyrrhotite.  Olivine phenocrysts are zoned from Fa_16.7 cores to Fa_43.3 rims, and pyroxene phenocrysts have irregular cores of orthopyroxene (as magnesian as Fs17.9Wo_2.4, with ~0.03 wt. % TiO₂ and ~0.4 wt. % Al₂O₃) mantled by pigeonite (Fs_25.4Wo_4.4 to Fs_37.0Wo_12.7) with minor subcalcic augite (Fs_21.7-24.0Wo _30.8-31.1). It is apparently not terrestrially paired to NWA 1195 and NWA 2046 (Irving et al., 2004b; 2005). Specimens: type specimen, 6.4 g, and one polished thin section, NAU; one polished thin section, UWS; main mass, Anonymous.