Northwest Africa 16977 (NWA 16977)

(Northwest Africa)

Purchased: 2024

Classification: Primitive achondrite (Brachinite)

History: Salek Mrabih purchased the 1758 g sample within a group of samples believed to be ordinary chondrites from a merchant in Tindouf, Algeria in 2024.

Physical characteristics: The exterior of the sample is coated with a dark-brown weathered fusion crust. Cut face shows a crystalline texture and FeS, rare metal and dark colored-opaque grains.

Petrography: Description and classification (A. Love, App): Sample shows a protogranular texture composed of (vol%): olivine (83) and twinned augite (7) and have an average grainsize of ~500 µm. Additional minerals are: troilite, chromite, rare orthopyroxene and apatite. Plagioclase is absent.

Geochemistry: (A. Love, App) olivine (Fa_30.8±0.4, Cr₂O₃ =0.1±0.2, Fe/Mn=60.7±2.4, n=20); low Ca-pyroxene (Fs_25.8±0.4Wo_2.0±0.2, Fe/Mn=39.3±1.3 n=3); high Ca-pyroxene (Fs_10.5±0.6Wo_43.3±0.4, Fe/Mn=32.4±4.0 n=7); Chromite (Cr#=83.5±0.2, Mg#=22.2±1.4, TiO₂ Wt%=1.3±0.0, n=5).

Classification: Primitive achondrite (Brachinite U-S2 low weathering) Based on textures and mineral chemistry, sample is a brachinite.

Specimens: Salek Mrabih (Dominions meteors) holds the main masses. A polished thin section and two sliced chunks weighing 21.2 g are on deposit at App.