Northwest Africa 6578 (NWA 6578)
Lunar meteorite (feldspathic breccia)
History: A tan to gray 1638 g stone was purchased in Morocco by Adam Aaronson in 2010.
Physical characteristics: Surface is deeply etched in some places from desert wind abrasion, and the gray colored areas show remnant, translucent fusion crust.
Petrography: (T. Bunch and J. Wittke, NAU; A. Irving and S. Kuehner, UWS): A fine-grained (<0.5 mm, mean grain size = 0.125 mm) partially annealed ultracataclastite (crushed matrix occupies > 90 vol%). The rock is an anorthosite based on the mineral modes of (vol%): anorthite 90, pigeonite 6, olivine 2, metal and FeS2. Numerous fine-grained (<0.02 mm) micrographic-textured patches contain pigeonite + olivine + plagioclase ± FeS and are roughly flow-oriented. In addition, glassy shock melt veins are sub parallel to the apparent flow direction. A few elongated clusters of vermiform taenite (<0.05 mm) are interspersed with micrographic intergrowths.
Geochemistry: Plagioclase, An94-96.3; pigeonite, Fs27.7-33.4Wo12.4-14, (FeO/MnO = 73-98); olivine, Fa21.7-44 (FeO/MnO = 78-90); taenite Ni = 9.8-16.7 wt. %. Shock melt glass (avg. of 3 in wt%) is SiO2 = 45.2, Al2O3 = 28.8, CaO = 18.9, FeO = 3.86, MgO = 2.12, Na2O = 0.4, TiO2 = 0.47, MnO = 0.18.
Classification: Achondrite (lunar, granulitic anorthositic breccia). This meteorite is one of the most feldspar-rich lunar specimens (rivaling some Apollo samples), but is texturally unique.
Specimens: A total of 20.2 g is on deposit at NAU. Mr. Adam Aaronson holds the main mass.
Northwest Africa 6578 Is a highly feldspathic granulitic breccia.
Meteoritical Bulletin Database
Korotev R. L. and Irving A. J. (2021) Lunar meteorites from northern Africa. Meteoritics & Planetary Science, 206–240.
Korotev R. L., Irving A. J., and Bunch T. E. (2012) Keeping Up With the Lunar Meteorites – 2012. 43rd Lunar and Planetary Science Conference, abstract no. 1152.