Northwest Africa 8486 (NWA 8486)

Morocco

Purchased: 2014 June

Classification: Ungrouped achondrite

History: Purportedly found at the same site as NWA 7325 near Bir el Abbas, Morocco. Acquired by CMS from Ruben Garcia in June, 2014.

Physical characteristics: A single, dark greenish stone (43.81 g), with one side showing chartreuse-colored fusion crust. Cut surfaces show almost equal amounts of bright, transparent, apple-green clinopyroxene (crystals to 3 mm) and milky white plagioclase (regions to 5 mm). The plagioclase contains abundant "clouds" of opaques heterogeneously distributed and concentrated. Vugs (to 2 mm) common within the plagioclase and at the plagioclase/clinopyroxene boundaries. Olivine, which is clear and glassy, is uncommon, occurring as grains to 1.5 mm and constituting <5 areal% of four examined surfaces.

Petrography: (L. Garvie, ASU) One polished mount (of 4 cm²) dominated by an apparent cumulate texture of diopside (Al and Cr-bearing) and calcic plagioclase. Pyroxene shows several sets of twin lamellae. Pyroxene/plagioclase grain boundaries show a micro-euhedral consertal texture of interdigitating euhedral plagioclase (to 10 μm) penetrating the pyroxene, and small "relict" micronmeter-sized grains of pyroxene in the plagioclase adjacent to the boundary. Olivine/plagioclase and olivine/pyroxene boundaries are sharp and smooth. Olivine show rounded and lobate-shaped grains. "Clouds" of micrometer-sized opaques (Cr-troilite and kamacite) locally common in the plagioclase. Accessory Cr-troilite, kamacite, and taenite, together with possibly weathered P-K-Si phases associated with the opaques.

Geochemistry: (L. Garvie, ASU) Clinopyroxene, Fs_1.15±0.03Wo_45.06±0.12, Al₂O₃=2.72±0.12 wt%, Cr₂O₃=0.98±0.02 wt%, n=11. Plagioclase, An_88.78±1.06Or_0.0, n=10. Olivine Fa_2.93±0.12, Cr₂O₃=0.37±0.01 wt%, CaO=0.34±0.01 wt%, FeO/MnO=39.3±9.1, n=10.

Classification: Ungrouped achondrite paired with NWA 7325 and NWA 8014.

Specimens: 43.81 g at CMS.