Northwest Africa 1817

Morocco

Purchased 2003 January

Mesosiderite

A complete stony-iron meteorite (728 g) was purchased in Rissani by a Moroccan dealer for N. Oakes (Oakes) in 2003 January.  Classification and mineralogy (A. Irving and S. Kuehner, UWS): Subequal amounts of metal and silicates in a coarse grained, unbrecciated, plutonic igneous texture.  Metal (about 40 vol%) is concentrated in spheroidal clusters interspersed with more silicate-rich material, and consists mainly of kamacite with included rounded taenite grains and rare schreibersite.  The remainder of the sample consists mainly of orthopyroxene (Fs₃₁Wo₂, FeO/MnO = 23.2-30.1) with lesser amounts of anorthitic plagioclase (An₉₂), irregularly-distributed olivine (~Fa₄₀, FeO/MnO = 42.3), a silica polymorph, troilite and chromite.  Oxygen isotopes (D. Rumble, CIW): replicate analyses of acid-washed pyroxene-rich fragments by laser fluorination, δ¹⁸O = 3.19, δ¹⁷O = 1.46, Δ¹⁷O = -0.22 ± 0.04 ‰.  This sample appears to be paired with NWA 1878.  Specimens: type specimen, 22.4 g, UWS; main mass, Oakes.