Northwest Africa 5289

Northwest Africa

Find: 2007

Iron (IVA)

History: A single iron mass was purchased from a Moroccan dealer in August 2007 by M. Graul (Bernau, Germany).

Physical characteristics: The 296 g mass, measuring approximately 81 × 54 × 30 mm, has a flattened shape. The portion of the surface originally sitting into the soil is partially covered with caliche deposit, whereas the remaining portion appears to be polished by wind-driven sand. No fusion crust is preserved.

Petrography: (M. D’Orazio, DST-PI) Widmanstätten pattern with kamacite lamellae (bandwidth = 0.32 ± 0.04 mm) and plessite fields in approximately 1:1 volumetric ratio. The kamacite lamellae show abundant Neumann bands and occasionally are displaced along shear planes. Accessory phases: schreibersite, troilite, chromite (tiny euhedral crystals included in troilite) and anhydrous Fe-phosphate (up to 1.3 mm in maximum length and surrounded by swathing kamacite).

Geochemistry: (M. D’Orazio, DST-PI) Composition of the metal (ICP-MS) is Co = 0.404, Ni = 9.02 (both in wt%), Cu = 111, Ga = 2.0, Ge < 1, As = 12.0, W = 0.36, Re = 0.08, Ir = 0.80, Pt = 3.76, Au = 2.33 (all in ppm).

Classification: Iron meteorite (IVA), fine octahedrite.

Type specimen: A 20.3 g etched endcut sample and 11.3 g of shavings are on deposit at DST-PI. M. Graul holds the main mass.