Grein 005        20°6’N, 10°37’E

Agadez, Niger

Purchased: 22 Dec 2015

Classification: Iron meteorite (IIIAB)

History: Found in November 2015 exposed on the surface by artisanal miners while prospecting for gold between Tehmet and Djado in the Tènéré Tafassasset. This is reportedly the second iron meteorite from the area. Six other masses with a total weight of 554 kg are likely from the same area, but neither find data nor sample material of these could be obtained, thus they are excluded from the reported mass.

Physical characteristics: The 52 kg mass is 39 × 25 × 18 cm and has the shape of a longitudinally split cone with the cone section showing minor concavity while the opposite surface is distinctly convex. Numerous regmaglypts measuring 1-3 cm across and 1-1.5 cm deep are present, and at least one troilite inclusion is observed. The specimen is coated with a thick layer of dark brown desert varnish.

Petrography: Polished sections display a well-developed Widmannstätten pattern of a medium octahedrite with a mean kamacite bandwidth of 1.0±0.2 mm. Neumann bands are visible within kamacite. Schreibersite and graphite are absent in the sections observed. Troilite is present in the form of rounded and bar-shaped inclusions ranging from 2-20 mm across the longest axis, partly surrounded by thin swathing kamacite. Fractures up to 1 mm wide penetrate the meteorite along the kamacite lamellae and are filled with terrestrial oxides, otherwise the interior weathering is very moderate. Fusion crust and heat-affected zones are mostly absent.

Geochemistry: ICP-MS data, using sample of North Chile (Filomena) as standard (C. Herd and G. Chen UAb): Ni = 8.0, Co = 0.51 (both wt%); Ir = 13.9, Ga = 22, Ge = 83, W = 1.4, Re = 1.4, Os = 7.3, Cu = 210, Ru = 12.7, Pd = 2.0, Pt = 15.7 (all μg/g).

Classification: (C. Herd, UAb): IIIAB iron, medium octahedrite.

Specimens: Type specimen consisting of two representative slices (67.6 and 49.4 g) at UAb. Main mass with S. Buhl.