Northwest Africa 7931 (NWA 7931)
Classification: Lunar meteorite (feldspathic breccia)
History: Purchased by Alexandre Debienne in May 2013 from a dealer in Agadir, Morocco.
Physical characteristics: A single small stone (5.92 g) lacking fusion crust.
Petrography: (A. Irving and S. Kuehner, UWS) Breccia consisting of numerous small mineral clasts in partly glassy, vesicular matrix. Minerals are anorthite, olivine, fayalite, pigeonite, ilmenite (with rare baddeleyite inclusions), Ti-rich chromite, troilite and minor kamacite.
Geochemistry: Olivine (Fa44.3-50.2; FeO/MnO = 85-96), orthopyroxene (Fs28.6Wo1.8; FeO/MnO = 60), pigeonite (Fs29.8-41.1Wo11.3-6.6; FeO/MnO = 52-62), ferroan subcalcic augite (Fs54.4Wo36.4; FeO/MnO = 63).
Bulk composition :(R. Korotev, WUSL): INAA of subsamples gave mean abundances of FeO 7.5 wt.%, and (in ppm) Sc 18, La 3.9, Sm 1.9, Eu 0.74, Yb 1.6, Th 0.6.
Classification: Lunar (feldspathic regolithic breccia).
Specimens: 1.2 g of material is at PSF. The remaining material is with ADebienne.
Northwest Africa 7931 is not big, but it appears to be unique. It’s most similar in composition to the NWA 8673 clan.
Meteoritical Bulletin Database
Korotev R. L. and Irving A. J. (2014) Keeping up with the lunar meteorites – 2014. 45th Lunar and Planetary Science Conference, abstract no. 1405.
Korotev R. L. and Irving A. J. (2021) Lunar meteorites from northern Africa. Meteoritics & Planetary Science, 206–240.
Sipiera P. P., Irving A. J., Kuehner S. M., Korotev R. L., and Debienne A. (2014) Petrology and composition of unpaired 5.9 gram lunar feldspathic regolithic breccia meteorite Northwest Africa 7931. 77th Annual Meeting of the Meteoritical Society, abstract no. 5198.