from The Meteoritical Bulletin, No. 112
Northwest Africa 15192 (NWA 15192)
Lunar meteorite (regolith breccia)
History: Purchased by Jay Piatek from Bachir Salek in 2022. Bashir Salek purchased it on August 11, 2021, in Western Sahara from a seller who acquired it from Touareg gold hunters that found it in northern Niger, likely on the Djado Plateau.
Physical Characteristics: Single spheroidal mass with faint regmaglypts and a flight-oriented shape, fusion crust is absent. Exterior is dark brown with scattered white feldspar clasts visible. Saw-cut polished-slice surfaces show fragments of white feldspar, orange to reddish tinted clasts, and dark shock melt veins and zones, all set in a gray-green, fine-grained groundmass.
Petrography: (A. Ross, C. Agee, UNM) Electron microprobe analysis and reflected light microscopy indicate a lunar fragmental breccia with mineral and lithic clasts to 3 cm. Some spheres were also observed. Major phases are plagioclase, clinopyroxene and olivine. Minor phases include Cr-spinel, ilmenite, and troilite. Approximately 10% of the lithic clasts contain significant alteration in which olivine has been transformed into an orange iddingsite-like phase. Microprobe mapping shows contact boundaries between unaltered olivine and iddingsite supporting a secondary alteration scenario. Iddingsite gave low microprobe totals indicating the presence of bound water. The iddingsite-bearing clasts and spheres are completely isolated and bounded by unaltered groundmass and this physical isolation from the exterior of the meteorite is not consistent with typical penetrative or crosscutting terrestrial weathering features. This alteration appears to have been present prior to the to the brecciation event that caused clast-forming fragmentation.
Geochemistry: (A. Ross, UNM) Plagioclase An96.5±0.4Ab3.2±0.4, n=4; olivine Fa29.9±8.0, Fe/Mn=95±9, n=8; clinopyroxene Fs28.0±17.0Wo15.8±13.9, Fe/Mn=56±12, n=6; iddingsite SiO2=27.7±2.8, Al2O3=12.1±1.1, MgO=21.0±1.6, FeO=23.3±0.9, total=85.8±2.4 (all wt%), n=2.
Classification: Lunar breccia with some clasts displaying features consistent with aqueous alteration. The presence of spherules indicate that this is a regolith breccia.
Specimens: 43 g on deposit at UNM plus a full polished slice on display at the UNM Meteorite Museum, Jay Piatek holds the main mass.
I have not studied Northwest Africa 15192.
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