Northwest Africa 13369 (NWA 13369)

Adrar, Algeria

Purchased: 2020

Classification: Martian meteorite (Shergottite)

History: The 24.7 g sample was found near Adrar and subsequently purchased in Tindouf. Fabien Kuntz purchased the sample in January of 2020.

Physical characteristics: The 24.7g sample is dark greenish-gray, crystalline and lacks fusion crust. The cut face shows the interior is composed of interlocking green crystals of pyroxene poikilitically enclosing black olivines (shock-darkened).

Petrography: Description and Classification: (A. Love, App) Sample has a poikilitic igneous texture composed of (vol%): 2.23 mm (avg. l.d., n=3) oikocrysts of pyroxene (~21.4) with 317 µm (avg. l.d., n=22) rounded chadacrysts of olivine. Oikocrysts are surrounded by 748µm (avg. l.d., n=20) euhedral prisms of olivine (~42.7); 913µm (avg. l.d., n=23); prismatic, twinned pyroxene (~45.7); and 488 µm (avg. l.d., n=23) lath-shaped maskelynite (~5.3). Additional minerals are merrillite, a Cl-apatite, chromite, ilmenite, titanomagnetite, pyrrhotite and secondary calcite.

Geochemistry: (A.Patchen-UTK) Olivine (Fa_33.0±3.3, Mg#67.1±3.3, Fe/Mn=49.2±2.0, n=96); low-Ca pyroxene (Fs_21.3±1.0Wo_3.3±0.8, Fe/Mn=30.7±1.2 n=32); pigeonite (Fs_27.9±2.7Wo_10.2±2.7, Fe/Mn=28.8±3.4 n=131); subcalcic augite (Fs_18.3±0.9Wo_28.8±1.1, Fe/Mn=25.2±1.1, n=8) augite (Fs_16.6±1.2Wo_34.1±2.3, Fe/Mn=25.4±1.4 n=51); plagioclase (An_52.0±4.6Or_1.6±0.5, n=16).

Classification: Martian (poikilitic shergottite). Based on mineral compositions (Fs, Wo, Mg# and Fe/Mn) and textures, this sample is a highly shocked (U-S5) poikilitic shergottite.

Specimens: Kuntz holds the main mass. A polished thin section and a sliced fragment weighing 5.71 g are on deposit at App.