Northwest Africa 15663 (NWA 15663)

(Northwest Africa)

Purchased: January, 2023

Classification: Ungrouped achondrite

History: The meteorite was purchased from a meteorite dealer in Mauritania.

Physical characteristics: Four light grayish to cream-colored fragments with patches of black fusion crust.

Petrography: Achondritic breccia composed of olivine (about 85 vol%), pyroxene (about 10 vol%), and accessories (about 5 vol%). Olivine and pyroxene are generally Mg-rich and present as euhedral to subhedral up to 2.5 mm sized mostly fragmented crystals. The vast majority of the grains are chemically homogeneous but show compositional differences between individual grains. A single zoned olivine grain and few exsolved pyroxenes were detected. Minor phases include silica, chromite, FeS, kamacite, and taenite. Contains augite-chromite and orthopyroxene-chromite symplectites. No feldspar found.

Geochemistry: compositions of individual olivine grains: Fa_8.9±0.1, FeO/MnO=38±3, n=10; Fa_13.6±0.1, FeO/MnO=38±3, n=10; Fa_18.6±0.1, FeO/MnO=38±2, n=10; Fa_23.9±0.1, FeO/MnO=40±2, n=10; zoned olivine: Fa_11.0±2.4 (Fa_8.6-14.1, FeO/MnO=40±4, n=10); compositions of individual low-Ca pyroxene grains: Fs_19.2±0.2Wo_3.8±0.6, FeO/MnO=22-25, n=10); Fs_23.8±0.1Wo_3.8±0.1, FeO/MnO=25-30, n=10); augite: Fs_5.1±0.1Wo_44.7±0.2 (Fs_4.8-5.3Wo_44.2-45.1, FeO/MnO=13-17, n=10); low-Ca pyroxene host to exsolution lamellae: Fs_37.3±0.7Wo_3.0±0.2 (Fs_36.2-38.0Wo_2.7-3.5, FeO/MnO=24-27, n=10); Ca-pyroxene exsolution lamellae: Fs_16.4±0.3Wo_41.1±0.5 (Fs_15.8-17.0Wo_40.5-41.8, FeO/MnO=19-22, n=10); chromite: Mg#47.2±0.3, Cr#74.3±0.3, n=7

Classification: Ungrouped achondrite, lherzolitic breccia. Likely paired with NWA 12217, NWA 12319, NWA 12562, NWA 13954, and NWA 14993.