Northwest Africa 7363 (NWA 7363)

Morocco

Purchased: 2019

Classification: HED achondrite (Eucrite, polymict)

Physical characteristics: The material is friable. Largest intact individuals are 315, 140, 71 and 36 g, some showing black fusion crust, and/or scattered orange-tan weathering and caliche staining. Numerous clasts up to 2 cm consist of conspicuously coarse, black-and-white shaded grains, in contrast with the stone’s finer grained, gray matrix.

Petrography: The rock is a polymict breccia with a finely granulated groundmass. Lithic clast textures range from aphanitic (but sprinkled with relict coarse grains) to gabbroic. A 1.5-cm clast, conspicuously leucocratic compared to the groundmass, is a eucrite uncommonly rich in fayalite. The fayalite is largely in the form of veins within coarse first-generation pyroxenes; the veins are nearly monomineralic but include traces of plagioclase and Cr-spinel, and are consistently surrounded by reaction zones of low-Mg/Fe pyroxene (cf. NWA 5073).

Geochemistry: Low-Ca pyroxene (34 analyses) ranges from Fs_30.7Wo_5.4 to Fs_59.8Wo_6.6. High-Ca pyroxene (4 analyses) clusters near Fs₂₇Wo_42. Pyroxene FeO/MnO (wt; 40 analyses) averages 31.2. Olivine (6 analyses, all from the aforementioned veins in the large eucrite clast) is Fa_62.7-66.3, average Fa_65.0+/-1.1. Plagioclase in the veins is anomalously Na-poor, An_96.8-98.7 (11 analyses). Elsewhere, plagioclase (31 analyses) is An_75.6-98.8, average An_92.5±3.7.

Classification: Although the texture indicates a polymict breccia, no diogenite component was found (so it is not a howardite). The meteorite is a polymict eucrite.

Specimens: 35 g at UCLA; main mass (5 kg) with Gessler.