Northwest Africa 12768 (NWA 12768)

Morocco

Purchased: September 2017

Classification: Iron meteorite (IIE)

History: A single 55 g stone purchased from a dealer in Alnif in September 2017.

Physical characteristics: The main mass is irregularly shaped, approximately 2.5 × 5 × 3 cm, with a mottled dark and light brown exterior.

Petrography: (C. Herd, L. Tunney, and R. Bukatiuk, UAb) Optical and SEM examination of a 1 × 2.5 cm polished and etched slice, as well as images of etched surfaces provided by the owner, show a well-developed micro-Widmanstatten pattern. Kamacite lamellae average 26±10 μm in width (n=89), but are individually comprised of equant subgrains with 120 degree junctions, suggesting recrystallization. Larger crystal boundaries are apparent at the cm scale, bounded by ~30 μm-wide kamacite lamellae. Inclusions were sought but not found.

Geochemistry: (C. Herd and L. Tunney, UAb) ICP-MS data, using sample of North Chile (Filomena) as standard: Ni = 8.8, Co = 0.47 (both wt%); Ir = 4.5, Ga = 25, Ge = 76, As = 14, W = 1.2, Re = 0.47, Pd = 3.9, Pt = 10, Cu = 316, Au = 1.2 (all µg/g).

Classification: Iron, IIE, finest octahedrite.

Specimens: Type specimen of 11.6 g at UAb. Main mass with Kuntz.