Northwest Africa 8736 (NWA 8736)

(Northwest Africa)

Purchased: Oct 2014

Classification: HED achondrite (Howardite)

History: Purchased by Habib Naji from a Moroccan meteorite hunter in Guelmin, Morocco, October 2014.

Physical characteristics: Single stone with weathered black fusion crust. A broken surface reveals a breccia with white clasts set in a fine-grained, light gray matrix; small (~1 mm) distinctive black CM fragments scattered throughout.

Petrography: (C. Agee, UNM) Microprobe examination of a polished mount shows a highly brecciated howardite with ~30% diogenitic pyroxenes, ~20% equilibrated cumulate eucrite pyroxenes, and ~50% equilibrated basaltic eucrite clasts. Howardite lithologies contain accessory Fe-Ni metal, troilite, chromite, silica, apatite, and ilmenite. CM2 xenoliths show moderate foliation, with scattered type I chondrules, ~70%, phyllosilicate-rich matrix, FeNiS phase, troilite.

Geochemistry: (C. Agee and N. Muttik, UNM) Diogenite orthopyroxene Fs_27.4±6.4Wo_2.4±0.3, Fe/Mn=30±2, n=7; cumulate eucrite low-Ca pyroxene Fs_45.7±4.4Wo_2.1±1.1, Fe/Mn=29±1, n=3, cumulate eucrite augite Fs_18.8Wo_41.8, Fe/Mn=23, n=1; cumulate eucrite pigeonite Fs_35.7±0.0Wo_14.8±0.8, Fe/Mn=28±2, n=2, basaltic eucrite low-Ca pyroxene Fs_61.0±4.0Wo_3.7±2.7, Fe/Mn=32±1, n=8; basaltic eucrite augite Fs_35.6±7.7Wo_42.1±0.5, Fe/Mn=37±3, n=2; basaltic eucrite pigeonite Fs_45.7Wo_18.3, Fe/Mn=31, n=1; plagioclase An_87.4±3.7, n=6. CM2 xenoliths: type I chondrule olivine Fa_2.3±1.1, Cr₂O₃=0.44±0.11 (wt%), n=6; ferroan olivine Fa_37.9, Fe/Mn=111, Cr₂O₃=0.40 (wt%), n=1; enstatite Fs_1.7Wo_0.7, n=1; aluminous augite Fs_1.9Wo_29.5, n=1.

Classification: Achondrite (howardite) with three lithologies: 1) diogenite, 2) equilibrated cumulate eucrite, 3) equilibrated basaltic eucrite. Xenolithic CM2 clasts are present throughout. Low weathering grade, high shock stage.

Specimens: 20.2 g including a probe mount on deposit at UNM, Habib Naji holds the main mass.