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.