Northwest Africa 15118 (NWA 15118)

Algeria

Find: 2021

Classification: Ungrouped achondrite

History: Purchased by Xu dengqin in 2022, reportedly found in Algeria 2021.

Physical characteristics: The meteorite is a single stone, weighing 230 grams, with one broken surface. The rest of the surface is covered with a white to light green translucent fusion crust with shrinkage cracks. The surface of the stone is covered with terrestrial clay.

Petrography: The meteorite is a fragmental breccia composed of mineral clasts of anorthite (up to 6 mm of grain size), orthopyroxene (up to about 100 µm), rare clinopyroxene, chromite, olivine and troilite. Anorthite is the dominant mineral, composed of over 94 vol% of the meteorite. Orthopyroxene is the second most abundant (~6 vol%) mineral in the meteorite. There are no exsolution lamellae of clinopyroxene in orthopyroxene. Minor clinopyroxene only occurs as veins (several to 10 µm in width) in large anorthite grains. Olivine is fairly rare, and only three grains with sizes range in 50-200 µm were observed in two observed sections. Chromite is present with less than 1 vol% in the meteorite and one to a few tens of µm in size.

Geochemistry: Plagioclase An_95.7±0.6Ab_4.1±0.6, n=52; orthopyroxene En_72.8±0.9Fs_24.8±0.9Wo_2.4±0.1, Fe/Mn=28.9±1.5, Mg#=74.6±0.9, n=46; clinopyroxene En_44.2±1.6Fs_10.0±0.7Wo_45.8±1.4, Fe/Mn=21.7±3.3, Mg#=81.5±1.4, n=10; olivine Fa_31.2±0.9, Fe/Mn=46.1±1.1, Mg#=68.5±0.7, n=10; chromite Chr69.2±2.9Spl27.0±2.9Usp3.8±1.4, Mg#=17.1±1.6, n=18. Oxygen isotopes Cao Xiaobin, Nanjing University): 3 acid-washed fragments analyzed by laser fluorination gave average δ¹⁸O= 3.770±0.111, δ¹⁷O=1.717±0.070, Δ¹⁷O=-0.243±0.014 (all per mil).

Classification: Achondrite, ungrouped