Northwest Africa 13031 (NWA 13031)

(Northwest Africa)

Purchased: 2018 Mar

Classification: Martian meteorite (Shergottite)

History: A group of four stones were found together at an unspecified location and purchased in Agadir, Morocco, by Aziz Habibi in March 2019.

Physical characteristics: The four stones (total weight 211 g) all have a distinctive light-green color. Fresh interiors exhibit sparse larger, lighter-colored macrocrysts in a predominant darker, finer-grained groundmass.

Petrography: (A. Irving, UWS and P. Carpenter, WUSL) Composed predominantly of a relatively fine grained assemblage (mean grainsize 0.3 mm) of polysynthetically-twinned, prismatic clinopyroxene and maskelynite with accessory Ti-free chromite, Ti-chromite, ilmenite, ulvöspinel, pyrrhotite, merrillite and silica polymorph. Very sparse macrocrysts (up to 2 mm) of orthopyroxene and pigeonite (with included olivine) are present, as well as rare very thin secondary calcite veinlets.

Geochemistry: Orthopyroxene macrocryst core (Fs_20.5Wo_3.2, FeO/MnO = 30), pigeonite cores (Fs_24.7-28.6Wo_8.5-10.4, FeO/MnO = 29-31, N = 2), high-Ca pyroxene rims (Fs_47.3-58.7Wo_14.1-19.3, FeO/MnO = 36-39, N = 3), olivine in pigeonite macrocryst (Fa_34.5-35.8, FeO/MnO = 50-56, N = 4), maskelynite (An_58.9-59.5Or_0.5-0.3, N = 2).

Classification: Shergottite (aphyric, pigeonite-rich with sparse macrocrysts).

Specimens: 20.1 g including one polished thin section at UWB; remainder with A. Habibi.