from The Meteoritical Bulletin, No. 108
Northwest Africa 6831 (NWA 6831)
History: The meteorite was purchased in 2009 from a local meteorite dealer in Erfoud, Morocco.
Physical characteristics: Dark greyish individual without fusion crust.
Petrography: (Ansgar Greshake, MNB) The meteorite is a relatively fine-grained fragmental breccia composed of up to 1 mm sized lithic and mineral clasts consolidated by a vesicular vitreous groundmass. Lithic clasts include basaltic and melt clasts; mineral clasts are dominantly calcic plagioclase, ferroan olivine, low-Ca pyroxene, pigeonite, and Ca-pyroxene. Minor phases include chromite, ilmenite, fayalite, and FeS.
Geochemistry: olivine: Fa40.7±5.5 (Fa31.7-50.4, n=25, FeO/MnO=82-102); low-Ca pyroxene: Fs23.7±0.2Wo3.5±0.3 (Fs23.5-24.0Wo3.2-4.0, n=5, FeO/MnO=55-66); pigeonite: Fs29.3±1.3Wo11.7±2.1 (Fs27.1-31.7Wo8.3-14.8, n=9, FeO/MnO=47-61); Ca-pyroxene: Fs60.7±3.6Wo24.5±2.0 (Fs54.6-67.3Wo20.1-26.9, n=9, FeO/MnO=66-75); calcic plagioclase: An92.6±1.3 (An90.1-93.8, n=20).
Classification: lunar (feldspathic breccia)
Specimens: Stefan Ralew.
I have not studied NWA 6831. The plagioclase is more albitic than is typical for a feldspathic lunar meteorite.
Meteoritical Bulletin Database