Northwest Africa 10019 (NWA 10019)

(Northwest Africa)

Purchased: 2015

Classification: Pallasite (ungrouped)

History: Purchased by Steve Arnold from Morocco in January 2015.

Physical characteristics: One 580 g fusion-crusted individual and 26 g of several small fusion-crusted pieces. Saw cuts and thin slices show angular orange-brown-green, translucent olivines, the largest 28 mm long, with many smaller (0.5-5 mm) angular grains, some of which are darker colored pyroxenes, all set in metal; only minor oxidation.

Petrography: (C. Agee, UNM) Microprobe examination of a polished mount shows approximately ~50% olivine, ~10% orthopyroxene, ~20% taenite, ~15% kamacite, minor calcic plagioclase, troilite, chromite, and calcium-magnesium phosphates.

Geochemistry: (C. Agee and N. Muttik, UNM) Olivine Fa_16.8±0.2, Fe/Mn=35±2, n=7; low Ca pyroxene Fs_15.4±0.2Wo_1.0±0.2, Fe/Mn=23±1, n=6; plagioclase An_75.9Ab_23.1Or_1.0, n=1; kamacite Fe=93.1±2.0, Ni=6.6±0.2, Co=0.61±0.03 (all wt%), n=4; taenite Fe=72.0±4.0, Ni=27.4±2.4, Co=0.19±0.05 (all wt%), n=5; troilite Fe=59.9, Ni=0.2, Co=0.1, S=35.2 (all wt%), n=1. Likely farringtonite Mg₃(PO₄)₂ and stanfieldite Ca₃Mg₃(PO₄)₄ detected in EDS, chromite also detected. Oxygen isotopes (K. Ziegler, UNM): acid-washed material analyzed in 11 replicates by laser fluorination gave, respectively δ¹⁸O= 3.286, 3.782, 3.878, 3.359, 3.548, 3.607, 3.935, 3.871, 3.817, 3.426, 3.516; δ¹⁷O= 1.479, 1.760, 1.760, 1.529, 1.635, 1.630, 1.846, 1.784, 1.763, 1.571, 1.599; Δ¹⁷O= -0.256, -0.237, -0.288, -0.245, -0.238, -0.274, -0.232, -0.260, -0.252, -0.238, -0.257 (linearized, all per mil).

Classification: Pallasite, ungrouped. This is a pyroxene pallasite with elevated Fa values similar to Fa in Springwater (PMG-an), ungrouped classification is based on oxygen isotope values similar to the PMG, but unlike any known pyroxene pallasite.

Specimens: 20.6 g including a probe mount on deposit at UNM, Steve Arnold holds the main mass