Northwest Africa 15312 (NWA 15312)

(Northwest Africa)

Find: Dec 2021

Classification: Lunar meteorite (melt breccia)

History: Edwin Thompson gave a 32.6 g slice to Cascadia for classification with the following information: He purchased the meteorite from a broker in Mauritania, who said that it was found in December 2021 near Agouémit, Mauritania; no geographic coordinates were obtained. The main mass has since been transferred to Paul Stahura.

Petrography: (M. Hutson, A. Ruzicka, Cascadia): In thin section, the sample is comprised of clasts ranging from single grain fragments <10 μm across to rock fragments up to 4 mm in length. Melt zones between clasts are dominantly feldspathic and cryptocrystalline, although an elongate stringer of brown glassy material (~3.5 × 0.7 mm) abuts one of the larger clasts. Fractures filled with a combination of feldspar and calcite cut across the section.

Geochemistry: Individual grains across the entire section were analyzed, along with two of the larger clasts. Excluding the larger clasts, olivine: Fa_28.4±5.2, Fe/Mn = 86.7±6.6, N=31; low-Ca pyroxene: Fs_21.0±5.0Wo_3.7±0.7, Fe/Mn = 50.1±4.6, N=27; pigeonite: Fs_30.5±6.0Wo_8.3±3.0, N=9; high-Ca pyroxene: Fs_15.1±5.1Wo_36.2±9.5, N=15; plagioclase feldspar: Ab_4.1±1.8Or_0.5±0.1An_95.4±1.8, N=17. Clast 4 (~2.2 × 1.7 mm) consists of roughly 60% feldspar (Ab_19.4±7.6Or_1.0±0.3An_80.1±8.0, N=11), 35% pigeonite (Fs_24.2±2.6Wo_11.5±7.4, N=2) and high-Ca pyroxene (Fs_17.4±0.6Wo_31.5±2.7, N=2), and 5% olivine (Fa_32.5±0.7, N=6). Clast 5 (~2.5 × 1.4 mm) consists of about 50% feldspar (Ab_7.7±1.7Or_0.6±0.3An_91.7±1.9, N=5), 30% olivine (Fa_22.3±0.6, N=4), and 20% low-Ca pyroxene (Fs_18.8±0.4Wo_2.8±0.4, N=4) and high-Ca pyroxene (Fs_8.6±0.5Wo_43.5±0.8, N=3).

Classification: This meteorite is best described as a lunar feldspathic clast-rich melt breccia base on texture and chemistry.

Specimens: Cascadia holds 26.8 g in one piece, as well as a polished thin section and material in an epoxy butt; Paul Stahura holds the main mass.