Northwest Africa 773

Western Sahara

Found 2000 September

Lunar Meteorite (cumulate olivine norite with regolith breccia)

Three stones of 359, 224 and 50 g, totaling 633 g were sold to Marvin Killgore (SWML) by nomads who showed him the place of find on a flat dry desert plain near Dchira, Western Sahara.  Mineralogy and classification (T. Fagan, UHaw; M. Killgore, SWML; J. Wittke and T. Bunch, NAU): consists of two distinct lithologies, cumulate rock and regolith breccia; shock stage, S2; weathering grade, W1. Cumulate portion: modes (vol%) are olivine = 54.7, pigeonite = 24.2, augite = 5, feldspar (including minor K-feldspar) = 15.6, opaques (troilite, chromite, Fe-metal, ilmenite) = 0.5; olivine, Fa_28–34, mean Fa₃₁, FeO/MnO = 99 ± 11 g/g; pigeonite, En₆₄Wo₁₁, FeO/MnO = 53 ± 6 g/g; augite, En₄₉Wo₃₆, FeO/MnO = 46 ± 6 g/g; plagioclase, An_88–91; Ba-rich K-feldspar, An₃Ab₄Or₉₃ with average BaO = 2.2 wt%. Breccia portion: contains fragments of cumulate portion as well as silica glass, hedenbergitic pyroxene, volcanic rocks, and unusual lithic clasts with fayalite + Ba-rich K-feldspar + silica + plagioclase; olivine and pyroxene in the breccia have a slightly wider compositional range towards lower Mg/(Mg + Fe) than in the cumulate portion of the rock. Chemical composition (D. Mittlefehldt, JSC): KREEP-rich with strong negative Eu-anomaly.  Noble gases (O. Eugster, Physikalisches Institut, Bern): high solar wind component, ₄He/₂₀Ne = 9, indicative of regolith material. Specimens: type specimen, 15 g, NHM; main mass SWML.