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
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.