Northwest Africa 11196 (NWA 11196)

(Northwest Africa)

Purchased: 2015

Classification: Iron meteorite (IAB-sLL)

Petrography: Sample has a high (25 vol%) FeS content. The troilite has squiggly shape with typical maximum dimensions in outcrop between 4 and 11 mm. Etching reveals well-defined kamacite, taenite and plessite but, in the section investigated, the metallic areas are too small (impinged by FeS) to define an octahedral structure. A rough estimate is that the kamacite bandwidth is in the range 0.5 to 0.8 mm.

Geochemistry: Chemical composition: Co, 4.72 mg/g; Ni, 84.6 mg/g; Cr 1380 μg/g, Ga, 57.8 μg/g; Ge, 283; As, 15.6 μg/g; W, 0.52 μg/g; Ir, 0.176 μg/g; Au, 1.538 μg/g.

Classification: The iron is compositionally a member of IAB-sLL-US. It has one near relative, GRO 06050; their elemental concentrations are mostly the same within experimental error; Ir in the NWA specimen ia about 14% higher, outside analytical error but within sampling error range for AB showers. GRO 06050 has abundant silicates and minor troilite, this new iron has abundant troilite and rare silicates. Both irons have >1000 μg/g Cr, much higher than those in other IAB-sLL-US members (Wasson and Kallemeyn, 2002; Wasson, 2011).