Northwest Africa 13855 (NWA 13855)

Algeria

Find: 2019

Classification: Iron meteorite (IAB-MG)

History: Collected by a nomad in an undetermined location in eastern central Algeria during the winter of 2019. Purchased by Geologist Juan Avilés Poblador in Spring 2019 on behalf of UAlic.

Physical characteristics: The meteorite is approximately 13 × 10 × 5 cm. Most of the outer surface is a metallic gray, with minor dark red-brown rust spots. The exterior surface is highly irregular and pitted with no fusion crust or regmaglypts present. Several cm-scale dark inclusions are apparent on most surfaces. The exterior surface texture suggests significant wind erosion and weathering.

Petrography: (J. Poblador, UAlic and C. Herd, UAb): SEM and hand specimen observations show sub-cm, equant kamacite grains with minor taenite laths. No inclusions were observed on cut surfaces but the cm-scale dark inclusions visible on the exterior surface are likely troilite. Weathering extends along grain boundaries into the interior.

Geochemistry: ICP-MS data, using sample of North Chile (Filomena) as standard (C. Herd, P. Hill, and S. DuFrane UAb): Ni = 6.5, Co = 0.46 (both wt%); Ir = 3.8, Ga = 90, Ge = 421, As = 11, Sb = 0.30, W = 1.2, Ru = 7.0, Re = 0.35, Os = 3.6, Pt = 8.3, Cu = 159, Au = 0.98 (all μg/g). Au value is a minimum due to uncertainties associated with the solution ICP-MS method.

Classification: (C. Herd, UAb): IAB iron, most likely MG when uncertainties on Au values are taken into account.

Specimens: Type specimen consisting of a 31.6 g representative slice at UAb. Main mass with Juan Poblador, 500 g with Sean Mchoney, 100 g with Topher Spinnato.