from The Meteoritical Bulletin, No. 108
Northwest Africa 12839 (NWA 12839)
History: Purchased by Ben Hoefnagels in June 2019 from a dealer in Agadir, Morocco.
Petrography: (A. Irving, UWS and P. Carpenter, WUSL) Diabasic texture (mean grainsize 0.5 mm). Composed primarily of zoned clinopyroxene and maskelynite with accessory blade-like ilmenite, very sparse zoned olivine (~3 vol.%), Cr-Ti oxides, baddeleyite, probable zirconolite, troilite, merrillite, silica polymorph, fayalite and hedenbergite. Dark shock glass is present in pockets (vesicular) and as cross-cutting veinlets.
Geochemistry: Subcalcic augite (core Fs28.8Wo26.3, FeO/MnO = 50; rim Fs72.4Wo23.6, FeO/MnO = 77), augite (core Fs21.2Wo38.7, FeO/MnO = 47; rim Fs81.5Wo17.7, FeO/MnO =81), pigeonite (core Fs41.8Wo12.9,FeO/MnO = 65; rim Fs69.8Wo22.4, FeO/MnO = 77), olivine cores (Fa37.6-39.5, FeO/MnO = 92-94, N = 3), olivine rims (Fa54.1-68.2, FeO/MnO = 93-110, N = 3), fayalite (Fa99.2, FeO/MnO = 95), maskelynite (An87.5-88.2Or0.3, N = 2).
Classification: Lunar (mare diabase, clinopyroxene-rich, olivine-poor).
Specimens: 14.1 g including one polished thin section at UWB; remainder with Mr. B. Hoefnagels.
I have not studied Northwest Africa 12839. I assume that it is unpaired with other basaltic lunar meteorites from the description. A diabase is a fine-grained volcanic rock solidified from a magma that, unlike a basalt, did not erupt onto the surface of a planet but beneath the surface.
Meteoritical Bulletin Database
Burney D., Neal C. R., Irving A. J., Carpenter P. K., Tepper J. H., and Hoefnagels B. (2020) Petrology and chemical composition of lunar mare diabase Northwest Africa 12839: Comparisons with Apollo basalts. 51st Lunar and Planetary Science Conference, abstract no. 2613.