Northwest Africa 8455 (NWA 8455)

(Northwest Africa)

Purchased: 2014

Classification: Lunar meteorite

History: Purchased from a Moroccan meteorite dealer in 2014.

Physical characteristics: Single stone, no fusion crust, irregular exterior with desert patina, freshly broken surface and saw cut reveals a few scattered millimeter-sized white feldspar clasts set in a very dark gray groundmass.

Petrography: (C. Agee, UNM) Microprobe examination of a polished mount shows this specimen to be a fragmental breccia composed of clasts (up to ~500 μm) of individual plagioclase, pyroxene, olivine grains, and also lithic clasts (up to ~1 mm) of gabbro and shock melt, set in a pervasive matrix of micrometer- to submicrometer-sized silicates. Accessory ilmenite, silica polymorph, chromite, phosphate, Fe-metal.

Geochemistry: (C. Agee and N. Muttik). Olivine Fa_26.6±3.5, Fe/Mn=100±9, n=28; pigeonite Fs_26.2±6.2Wo_8.7±4.4, Fe/Mn=58±5, n=22; augite Fs_21.5±8.4Wo_34.5±6.8, Fe/Mn=55±11, n=11; plagioclase An_95.1±1.0Ab_4.5±1.0Or_0.4±0.1, n=4. Shock melt (proxy for bulk composition) SiO₂=44.6±1.1, TiO₂=0.59±0.53, Al₂O₃=26.1±3.2, Cr₂O₃=0.10±0.03, MgO=6.8±1.8, FeO=5.0±1.3, MnO=0.04±0.03, NiO=0.02±0.01, Na₂O=0.69±0.20, K₂O=0.19±0.04 (all wt%).

Classification: Achondrite (lunar feldspathic breccia)

Specimens: 20.5 g, including a probe mount is on deposit at UNM. J. Piatek holds the main mass.