Northwest Africa 8535 (NWA 8535)

(Northwest Africa)

Purchased: 2014 Mar 6

Classification: Angrite

History: Purchased by Habib Naji in Guelmin, Morocco, 6 March 2014, from a nomad who reportedly found the meteorite at Tazounte, ~100 km east of Guelmim.

Physical characteristics: Single stone. Exterior with patches of black fusion crust, coarse green crystals up to several mm, scattered mm-sized vugs, broken surface reveals bright green crystalline texture with some dark grains, fresh.

Petrography: (C. Agee, UNM) Microprobe examination of a polished mount shows approximately 90% olivine and ~5% fassaite. Olivines are zoned with Fe-enriched rims, olivine rims are also Ca-enriched, average grain size ~700 μm, triple junctions commonly occupied with fassaite. Accessory aluminous-spinel, chromite, troilite, kamacite, and taenite.

Geochemistry: (C. Agee and N. Muttik, UNM) Olivine Fa_19.4±5.8, Fe/Mn=88±2, CaO=0.39±0.41 (wt%), Cr₂O₃=0.23±0.13 (wt%), n=24; fassaite Fs_11.1±0.8Wo_56.0±1.7, Fe/Mn=86±19, Al₂O₃=13.85±2.71 (wt%), TiO₂=1.9±0.4 (wt%), n=12. Oxygen isotopes (K. Ziegler, UNM): acid-washed material analyzed in 3 replicates by laser fluorination gave, respectively δ¹⁸O = 2.589, 3.925, 3.761; δ¹⁷O = 1.297, 1.934, 1.877; Δ¹⁷O = -0.070, -0.138, -0.109 (linearized, all per mil).

Classification: Dunitic angrite, with possibly the most magnesian olivines of any known angrite. Δ¹⁷O oxygen isotope values are within the typical angrite range, however one analysis had anomalously low δ¹⁷O and δ¹⁸O.

Specimens: 20.5 g including a probe mount on deposit at UNM, H. Naji holds the main mass.