Northwest Africa 1109 - Polymict Eucrite Breccia

Northwest Africa 1109
Polymict Eucrite Breccia

This meteorite has an overall light tan to pale brown color depending on extent of weathering, but all show distinctive white and grey mineral and lithic clasts in a light tan matrix Classification and mineralogy (A. Irving and S. Kuehner, LTWS): Polycrystalline clasts include basaltic eucrites (ophitic texture, variable grain size, mainly anorthite+pigeonite Wol6Fs57, FeO/MnO = 30), cumulate eucrites (coarse grained, equigranular, mainly anorthite+exsolved pigeonite with accessory silica), rare eucritic breccias, and distinctive ferroan intergrowths (very fine-grained, "eutectoid" aggregates of intergrown fayalite+hedenbergite+silica+troilite, which appear to be quenched igneous mesostasis; some examples are associated with anorthite phenocrysts, and others appear to have partially replaced exsolved pigeonite grains). Mineral clasts include homogeneous pigeonite grains (e.g., Wol5Fs31, FeO/MnO = 26), pigeonite grains with clinopyroxene exsolution lamellae (FeO/MnO = 30-33), anorthite and a silica polymorph. Orthopyroxene typical of diogenites was searched for but not found (thus this sample is not a howardite). Accessory minerals in clasts and matrix include ilmenite, Ni-free Fe metal, chromite, baddeleyite and apatite. Specimens: type specimen, 20 g, and four polished thin sections, UWS; main mass, Hupe.