Northwest Africa 1457

Morocco

Purchased 2001 December

Achondrite (winonaite)

Seven small stones with a total weight of 52 g were purchased from a Moroccan dealer by A. and G. Hupé (xHupé) in 2001 December. Classification and mineralogy (A. Irving and S. Kuehner, UWS): medium-grained, equilibrated metamorphic texture with triple junctions among mineral grains. Abundant enstatite (Fs6Wo1.5, FeO/MnO = 15) and forsteritic olivine (Fa5, FeO/MnO = 18) with subordinate diopside (Fs2.8Wo44, FeO/MnO = 8), sodic plagioclase (Ab82Or4), Ni-poor Fe-Ni metal, troilite, schreibersite, Cr-rich chromite, and Cl-rich apatite. Daubreelite occurs as blades within some troilite grains. Rare chromite grains (up to 20 µm; 66 wt% Cr2O3; Cr/ (Cr+Al) = 0.870; Mg/(Mg+Fe) = 0.682) are associated with troilite. Grain boundaries are veined by heterogeneous Ni­free iron oxides and/or hydroxides. Oxygen isotope composition (D. Rumble, CIW): analyses of two whole rock fragments by laser fluorination gave δ¹⁸O = +5.1 ± 0.1‰; δ¹⁷O = +2.3 ± 0.1‰; ∆¹⁷O = –0.40 ± 0.03‰. The texture, mineralogy and oxygen isotopic composition of this sample match the criteria for winonaites given by Benedix et al. (1998). Specimens: type specimen, 10 g, and one polished thin section, UWS; main mass, xHupé.