Northwest Africa 6687 (NWA 6687)
Lunar (feldspathic breccia)
History: Found in Morocco in 2010 and purchased from the finder by G. Tomelleri.
Physical characteristics: A single black stone (42.4 g) lacking fusion crust. The interior is dark gray and displays several small white clasts.
Petrography: (V. Moggi Cecchi, S. Caporali, G. Pratesi, MSP) The overall texture consists of coarse-grained inclusions set in a fine-grained matrix. The matrix contains isolated mineral clasts, mainly consisting of augite, plagioclase and olivine, and a fine grained mineral debris enclosed within a dark, partly glassy and vesicular matrix. The large coarse grained inclusions consist of elongated plagioclase and clinopyroxene crystals set in a glassy matrix. Opaque phases are represented by ilmenite, ulvospinel and chromite.
Geochemistry: Olivine (Fa33.7-49.2, Fe/Mn=108, n=20, Cr=1500 ppm, Mn=3100 ppm), augite (Fs23.8.5-31.2En24.9-30.0Wo27.3-30.0Al-px 13.9-19.5; FeO/MnO mean=65.6; V=400 ppm; Ca=0.61 afu), plagioclase (An83.4Or0.8; K = 0.008 afu); Oxygen isotopes: (I. Franchi, R. Greenwood, OU) δ17O = 3.58, δ18O = 6.84, Δ17O = 0.02 per mil.
Classification: Achondrite (lunar, feldspathic breccia).
Specimens:9.5 g sample is on deposit at MSP.
Northwest Africa 6687 is described as a feldspathic breccia above. With 16% FeO, however, this meteorite is one of the least feldspathic of the brecciated lunar meteorites. Compositionally, it’s a 2:1 mixture of mare basalt and KREEP impact-melt breccia. In that regard, it’s most similar to the Apollo 12 soil and unlike any other lunar meteorite.
Meteoritical Bulletin Database
Korotev R. L. and Irving A. J. (2021) Lunar meteorites from northern Africa. Meteoritics & Planetary Science, 206–240.
Moggi-Cecchi V., Caporali S., Pratesi G., and Franchi I. A., and Greenwood R.C. (2012) NWA 6687: A new lunar meteorite from northwest Africa. 42nd Lunar and Planetary Science Conference, abstract no. 2710.