Northwest Africa 595

Morocco

Purchased 2001 January

Primitive achondrite (brachinite)

One complete stone of a total weight of 196 g was purchased by Cott in Tucson, Arizona, in 2001 January.  Mineralogy and classification (P. Warren, UCLA): mineral mode, 80 vol% olivine, 10–15 vol% orthopyroxene, 5–10 vol% augite and minor chromite, traces include kamacite and Ni-rich metal, no plagioclase was found.  Mineral composition, olivine, Fo_71–72 and FeO/MnO = 52 ± 6, orthopyroxene, En_72–73Fs_25–26Wo_2.2 and FeO/MnO = 40 ± 7, augite, En₄₅Fs_10–11Wo_44–45 and FeO/MnO = 32 ± 9, chromite, Cr/(Cr + Al) = 0.77, Mg/(Mg + Fe) = 0.25 and TiO₂ = 1.1–1.4 wt%. Typical polygonal-granular texture with a notable alignment of more elongated grains; grain sizes of 0.5 to 1 mm, one exceptionally large grain of 3 mm was observed. Highly weathered, W3/4. Texture, mineral mode and mineral composition of mafic silicates and bulk chemical data are consistent with its classification as brachinite. Specimens: type specimen, 23 g, and thin section, UCLA; main mass, Cott.