Northwest Africa 15367 (NWA 15367)

(Northwest Africa)

Find: Nov 2021

Classification: Lunar meteorite (melt breccia)

History: Edwin Thompson gave a 28.4 g slice to Cascadia for classification with the following information: A single 2238 g mass was found in Nov. 2021 in or near Bassikounou, Mauritania.

Physical characteristics: Physical Characteristics: Gray, cream, and white colored clasts set in a dark gray/black background are visible on the cut face of the slice received by Cascadia, with a rough alignment of elongate clasts. The largest clast in the slice (~1.5 cm × 0.7 cm) is light gray and contains both white and dark gray/black sub-clasts.

Petrography: (M. Hutson, A. Ruzicka, D. Sheikh, Cascadia): Sample is a melt breccia consisting of sub-angular to sub-rounded lithic and mineral clasts set in a glassy matrix. Lithic clast lithologies identified in the sample are primarily highland lithologies and include: anorthosites, anorthositic troctolites, gabbroic anorthosites, and noritic anorthosites (Stoffler et al., 1980). Accessory phases include Cr-spinel and ilmenite.

Geochemistry: (M. Hutson, D. Sheikh, A. Ruzicka, Cascadia; P. Carpenter, WUSL): Average of all data: Plagioclase feldspar: Ab_3.6±0.9Or_0.4±0.2An_96.0±0.9, N=131; Olivine: Fa_32.6±7.1, Fe/Mn=94.7±8.8, N=39; Low-Ca pyroxene: Fs_26.6±8.2Wo_3.6±0.7, Fe/Mn=57.0±3.9, N=29; Pigeonite: Fs_30.9±5.8Wo_9.3±2.9, N=34; Augite: Fs_14.1±5.1Wo_39.6±2.9, N=27.

Classification: Lunar (melt breccia). This meteorite is best described as a lunar feldspathic melt breccia based on texture and chemistry.

Specimens: Cascadia holds 25.7 g in five pieces, as well as a polished thin section and material in an epoxy butt; Thompson holds the main mass.