Northwest Africa 11591 (NWA 11591)

Algeria

Purchased: 2016 May 1

Classification: HED achondrite (Eucrite)

History: Purchased by Miao Bing-an in 2016 in Morocco.

Physical characteristics: The fusion crust has been largely weathered from the surface of the sample. In the area where it remains, it is thin (<0. 5mm) and shiny black. The interior of the stone is medium gray and contains inclusions that range from whitish-gray to black. There are several clasts and small fractures in the stone. A small amount of oxidation is present in the interior of the sample. The sample is approximately 6.8 × 8.6 × 3.8 cm.

Petrography (L.Huang, B. Miao, H. Chen, GUT): This meteorite is a pigeonite-plagioclase rock with fine to medium grain size. Breccia composed of mineral and lithic fragments set in a fine-grained, generally fragmental matrix. Lithic clasts are generally ophitic with medium-grained pyroxenes and skeletal plagioclase grains (width ~30-200 μm) and a fine-grained recrystallized mesostasis. Pyroxene generally contain pigeonite with augite lamellae (width ~3 μm). A silica phase is commonly present. Accessories are ilmenite, chromite, troilite and rare phosphate (apatite and merrillite.

Geochemistry (L. Huang, B. Miao, H. Chen, GUT): Bulk pyroxene: Fe/Mn=30.2; Low-Ca pyroxene: median compositions are Mg#=36.5; Fs_58.2Wo_8.4 (n=30). augite lamellae: median compositions are Mg#=40.1, Fs_43.9Wo_26.7 (n=25). Plagioclase: An_86.0Or_0.7 to An_92.4Or_0.4.

Classification: Basaltic polymict brecciated eucrite

Specimens: 35.1 g and polished thin section are deposited in GUT