Northwest Africa 15432 (NWA 15432)

(Northwest Africa)

Purchased: Sep 2021

Classification: Lunar meteorite (melt breccia)

History: Meteorite was purchased by Mr. Jasper Spencer from a Mauritanian dealer in September 2021 via Facebook Messenger, who said it was found in Algeria in 2021. Mr. Spencer sent a 4 g end piece to Cascadia for classification.

Physical characteristics: Physical Characteristics: The cut face shows small (< 1mm across) angular light-colored to white clasts set in a black background; only two rectangular clasts exceed 1mm across (both are ~1.5 × 0.75 mm in exposed area).

Petrography: (M. Hutson and A. Ruzicka, Cascadia): Sample is a melt breccia consisting of sub-angular to sub-rounded lithic, mineral and glass clasts set in a glassy matrix. Clasts are dominated by anorthitic feldspar; the largest (~1.5 × 0.75 mm) is a noritic anorthosite (Stoeffler et al., 1980). One clast (~0.7 × 0.5 mm in exposed area) is composed of anorthitic feldspar, orthopyroxene, clinopyroxene, and olivine in the proportions described by Stoffler et al. (1980) as an anorthositic norite, but ~5% of the clast is comprised of coarse (50-100 µm across) irregularly-shaped troilite. Other accessory phases include Cr- and Al-rich spinel grains, SiO₂, FeNi metal, and ilmenite.

Geochemistry: Plagioclase feldspar: Ab_3.2±0.7Or_0.5±0.1An_96.2±0.8, N=19. Olivine grains within clasts were relatively uniform, but varied from clast to clast (Fa_28-41). Mg-rich olivine grains (Fa_6.2-7.5) were observed as individual grains between clasts. Average of all olivine grains: Fa_27.9±14.3, Fe/Mn=92.0±9.3, N=13. Low-Ca pyroxene: Fs_32.4±0.8Wo_3.4±0.5, Fe/Mn=59.2±6.0, N=6; Pigeonite: Fs_34.9±11.7Wo_9.4±3.7, N=16; Augite: Fs_22.9±5.3Wo_31.3±6.1, N=9.

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

Specimens: Cascadia holds 2.6 g in one piece, as well as a polished thin section and material in an epoxy butt; Mr. Jasper Spencer holds the main mass.