Northwest Africa 13856 (NWA 13856)

Algeria

Purchased: 2020

Classification: Achondrite (ungrouped)

History: Fabien Kuntz purchased the 374.3 g sample from a meteorite prospector in Tindouf, Algeria, in 2020.

Physical characteristics: Sample has an irregular shape and a dark-brown exterior. The cut face shows a crystalline interior crosscut by black veins.

Petrography: Description and classification (A. Love, App) Sample shows poikilitic texture composed of (vol%): 1.5mm (n=12) orthorhombic pyroxene oikocrysts (30), anhedral-subhedral olivine (49) occurring as 76 µm (n=11) chadacrysts and 230 µm (n=23) phenocrysts and interstitial plagioclase (13). Lath-shaped pyroxenes share a preferred orientation and some are mantled with Ca-rich pyroxene. Vugs and vesicles occur within plagioclase. Chondrules are absent. Additional minerals are: albitic plagioclase with acicular inclusions of pyroxene, rare troilite, Ti-chromite, apatite, FeOH. Sample vestiges or relict chondritic-textured lithologies; evidence of rapid growth textures (cellular metal-sulfide mixtures, or spherical metal droplets).

Geochemistry: Olivine (Fa_23.9±0.3, Fe/Mn=45.6±0.7, n=10); low-Ca Pyroxene (Fs_20.0±0.8Wo_3.9±1.5, Fe/Mn=28.2±0.7, n=12); high-Ca pyroxene (Fs_13.1±0.7Wo_33.5±2.2, Fe/Mn=22.1±0.6, n=5); plagioclase (Ab_85.9±2.2Or_3.5±0.6, n=6). Oxygen Isotopes: (Karen Ziegler, UNM) analyses of acid-washed subsamples by laser fluorination gave (all per mill): δ¹⁷O=3.536, 3.786, 3.682; δ¹⁸O=4.647, 5.172, 4.947; Δ¹⁷O=1.082, 1.055, 1.070.

Classification: Achondrite (ungrouped) strong shock, moderate weathering. Sample shows cumulate igneous texture, pyroxenes with compositional zoning and has mineralogic and isotopic similarities to L ordinary chondrites.

Specimens: Fabien Kuntz holds the main mass. An endcut weighing 32.12g and a polished thin section are on deposit at App.