Official Meteoritical Bulletin entry for Northwest Africa 4468:
Northwest Africa 4468 Northwest Africa Find: Summber 2006 Achondrite (Martian, basaltic shergottite)
History: Found in the western part of the Sahara in summer 2006 and purchased in Laâyoune by G. Hupé in July 2006. Physical characteristics: A single 675 g ellipsoidal stone, mostly coated by shiny black fusion crust, and broken at one end revealing the pale yellow-green interior. Petrography: (A. Irving and S. Kuehner, UWS) Large ovoid pyroxene oikocrysts (2–10 mm across) enclosing chadacrysts of Ti-poor chromite and olivine are set in an interstitial matrix of 35% olivine, 30% clinopyroxene, 25% maskelynite (all vol%), Ti-chromite, ilmenite, merrillite, Cl-apatite (as prisms up to 0.8 mm long), and pyrrhotite. Inclusions (up to 300 µm across) surrounded by radial shock relaxation fractures occur within matrix olivine grains; some are quenched melt inclusions and others consist mainly of maskelynite. The specimen is cross-cut by sporadic, thin, dark, glassy shock veins (Irving et al. 2007). Mineral compositions and geochemistry: Pyroxene oikocrysts are zoned from orthopyroxene cores (Fs24.5Wo4.4; FeO/MnO = 35.4) with mantles of pigeonite (Fs26.3Wo6.3; FeO/MnO = 29.4) to augite rims (Fs17.9Wo33.6; FeO/MnO = 24.9). Olivine chadacrysts (as magnesian as Fa28.8) typically become progressively more ferroan from pyroxene core to rim (up to Fa39.9). Matrix olivine (Fa40.7; FeO/MnO = 50.2), matrix clinopyroxene (Fs31.3Wo8.1, Fs19.6Wo31.3), matrix maskelynite (An38.7–54Or3.9–2.3); maskelynite in inclusions within olivine is inhomogeneous and K-Na-rich (Or52.6Ab40.7An6.7). Classification: Achondrite (Martian, basaltic shergottite). Type specimen: A total of 20.2 g and one large 3.8 × 2.8 cm thin section are on deposit at UWS. G. Hupé holds the main mass.
Scientific abstracts and news regarding NWA 4468:
L. E Borg, A. M. Gaffney, and D. DePaolo
(2008) PRELIMINARY AGE OF MARTIAN METEORITE NORTHWEST AFRICA 4468 AND ITS
RELATIONSHIP TO THE OTHER INCOMPATIBLE-ELEMENT-ENRICHED SHERGOTTITES.
Lunar and Planetary Science XXXIX. (abs. 1851). http://www.lpi.usra.edu/meetings/lpsc2008/pdf/1851.pdf