Northwest Africa 10783 (NWA 10783)

(Northwest Africa)

Purchased: 2015 May 1

Classification: Lunar meteorite (anorth)

History: Found in the Almahbas region near the frontier between Morocco and Algeria.

Physical characteristics: The stone is a breccia with no visible fusion crust. The type specimen is mostly light colored with metal specks, and there is a dark zone at one end.

Petrography: (R. Hewins, S. Pont, B. Zanda, MNHNP) Most of the prepared section is a poikilitic anorthosite resembling Apollo 77017. It consists of plagioclase phenocrysts up to 2 mm in length set in pyroxene poikilitic to stubby tiny plagioclase laths (down to 20 μm) and to olivine granules (~50 μm). Both pigeonite and augite are present, but with no obvious exsolution. Minor minerals include chromite, ilmenite, baddeleyite, taenite and kamacite. There is a dark sliver of breccia matrix at the end of the section containing a huge variety of clast types, 1 mm or smaller. These include crystal clasts (olivine, pigeonite, augite, anorthite, chromite and a silica polymorph), breccia clasts, and lithic clasts often with elongated plagioclase laths.

Geochemistry: Mineral compositions and Geochemistry: (R. Hewins and S. Pont, MNHNP) The olivine composition is Fa_34.1±1.5, with FeO/MnO 119±14. Pyroxenes are pigeonite Fs_25.4Wo_11.1 and augite En_49.6Fs_19.2Wo_31.2. Plagioclase is An_94.0±0.6Ab_5.5±0.6Or_0.5±0.2. Taenite contains ~37% Ni. Mineral compositions are similar to those of Apollo 77017, but olivine is a little less ferroan.

Classification: (R. Hewins MNHN, L. Labenne Paris) Lunar poikilitic anorthositic breccia.

Specimens: The type specimen consists of 3.78 g and 0.63 g at MNHNP. The remaining 17.6 g minus sawdust has been sold in the form of thin slices by Labenne.