Northwest Africa 14242 (NWA 14242)

(Northwest Africa)

Purchased: 2020 Sept

Classification: Iron meteorite (IAB, ungrouped)

History: The single, 21 g stone was reportedly found in Algeria in August 2020. Purchased by Juan Chen and Shun-Chung- Yang from a dealer residing in Tindouf in September 2020. Dr. Celestian, NMHLA made the primary assessment by XRF analysis indicating it an iron meteorite.

Physical characteristics: The roughly ellipsoid meteorite is approximately 2.5 × 1.5 × 1.5 cm and has a reddish-brown exterior. Cut surfaces reveal several inclusions that are square in cross-section, and between 5 and 8 mm across. The inclusions are mostly clustered to one side of the interior with some corners are in contact with one another.

Petrography: (C. Herd and P. Hill, UAb; E. Walton, MacEwan U) Petrographic investigation by scanning electron microscopy at UAb and Raman spectroscopy at MacEwan U show that the main metallic portion is composed of lozenge-shaped kamacite and ~20 μm sized schreibersite swathed in kamacite, set in a matrix of taenite. The inclusions have an hourglass-shaped center area composed of a fine-grained (<15 μm) intergrowth of equant silica and interstitial graphite. Marginal to the silica-rich center areas, the inclusions are composed of irregular, 50-100 μm taenite and schreibersite grains intergrown with kamacite. This kamacite hosts laths of graphite that are up to 5 μm across and 15 μm long. Raman confirmed the presence of graphite but was not able to identify the silica phase. No terrestrial alteration was observed.

Geochemistry: ICP-MS data, using sample of North Chile (Filomena) as standard (C. Herd, P. Hill, and S. DuFrane UAb): Ni = 11.0, Co = 0.49 (both wt%); Ir = 1.1, Ga = 61, Ge = 220, As = 16, Sb = 1.3, Ru = 4.6, Re = 0.09, Os = 1.0, Pt = 4.5, Cu = 426, Au = 1.5 (all μg/g). Au value is a minimum due to uncertainties associated with the solution ICP-MS method.

Classification: (C. Herd, UAb): IAB iron, ungrouped. Element concentrations fall between the MG and sLM subgroups of Wasson and Kallemeyn (2002). Ungrouped based on texture and mineralogy.

Specimens: Type specimen consisting of a 5.3 g representative piece at NHMLA. Additional 1.65 g slice, from which trace elements were obtained, at UAb. Main mass with Shun-Chung Yang.