Northwest Africa 6167 (NWA 6167)

(Northwest Africa)

Purchased: 2003

Classification: Iron meteorite (ungrouped)

History: A single iron mass was purchased in Erfoud, Morocco, in December 2003, by F. Kuntz (Besançon, France).

Physical characteristics: The 500 g mass, measuring about 7 × 4 × 4 cm, has a bullet-shaped morphology with some regmaglypts and remnants of the fusion crust.

Petrography: (M. D’Orazio, M. Gemelli, DST-PI) Etched sections show an ataxitic texture. Under high magnification the metal shows a very fine (1-5 µm) intergrowth of kamacite and taenite arranged into a micro-Widmanstätten pattern. Small globular inclusions (to 2 mm) of sulfide-rich material are scattered in the metal. These inclusions are made of a heterogeneous intergrowth of very small (1-10 µm) crystals of kamacite, taenite and schreibersite with interstitial troilite. Some of these inclusions also host small euhedral elongated crystals of chromite. The studied 16.5 cm² surface contains five rounded silicate inclusions (to 6.8 mm). They consist of prevailing crystals of olivine (Fo_79.6±0.6), low-Ca pyroxene (En_78-80 Wo_2.2-3.1), high-Ca pyroxene (En_49-51 Wo_41-42), plagioclase (An_78-85), Ca-phosphate and chromite. Close to the boundary with the Fe-Ni metal, the silicate crystals are crossed by tiny veinlets of very fine-grained Fe-Ni metal+troilite or iron oxyhydroxides.

Geochemistry: Composition of the metal (ICP-MS; D’Orazio and Folco, 2003) is: Co = 0.929, Ni = 19.0 (both in wt%), Cu = 302, Ga = 11.3, Ge = 51.4, As = 14.5, W = 2.68, Re = 1.73, Ir = 18.7, Pt = 26.4, Au = 1.12 (all in ppm). Reference: D’Orazio, M. and Folco, L. (2003). Chemical analysis of iron meteorites by inductively coupled plasma - mass spectrometry. Geostandards Newsletter, 27, 3, 215-225.

Classification: Iron meteorite (silicated), Ni-rich ataxite, ungrouped, very low weathering grade.

Specimens: One 21.79 g polished full slice is on deposit at DST-PI.  Kuntz holds the main mass.