Northwest Africa 6716 (NWA 6716)

(Northwest Africa)

Purchased: 2010 Aug

Classification: Iron meteorite (IIE)

History: A single iron mass was purchased from a Moroccan dealer in August 2010 by M. Graul, Bernau, Germany.

Physical characteristics: The 293 g wedge-shaped mass measures 110 × 35 × 5-30 mm and has a glossy-brown external surface.

Petrography: (M. D’Orazio, A. Fazio, DST-PI) Etched section show a polycrystalline texture composed of 0.1 to 2 mm grains of kamacite often showing 120° triple junctions and Neumann bands. Ghosts of the pre-existing Widmannstätten pattern (bandwidth = 1.5±0.2 mm) visible. Plessitic fields showing comb-net texture are preserved. The sections show three large (to 4.5 mm) rounded inclusions of Cl-rich Ca-phosphate, with rims of Cl-free Ca-Mg-Na-phosphate and tiny inclusions of Cl-free Mg-Ca-Fe-Na-Mn phosphate. Schreibersite is relatively common as elongated (to 8 mm) skeletal crystals. A well-preserved heat-alteration zone is marked by an 1.5-2.0 mm-thick band showing serrated texture and grain-size (50-100 μm) significantly smaller that the meteorite interior. Terrestrial weathering is low.

Geochemistry: Composition of the metal (ICP-MS; D’Orazio and Folco, 2003) is Co=0.422, Ni=7.77 (both in wt%), Cu=147, Ga=24.3, Ge=62, Ir=4.4, Au=0.97 (all in ppm).

Classification: IIE iron meteorite, recrystallized coarse octahedrite.

Specimens: A 12.7 g etched end cut and a 9.3 g polished full slice are on deposit at DST-PI. MGraul holds the main mass.