Meteoritical Bulletin: Entry for Nova 057

Writeup from MB 108:

Nova 057

Baja, Mexico

Find: 1984

Classification: Iron meteorite (IIAB)

History: Purportedly found in Baja California, Mexico, in 1984

Physical characteristics: The 26.5 kg meteorite is oblong, with a red-brown exterior, regmaglypts of varying size, and measures approximately 40 cm × 18 cm × 15 cm.

Petrography: (C. Herd, UAb) Optical investigation of a small (~1.5 × 2.0 cm) polished and etched slice reveals a Widmanstaetten pattern consistent with a coarsest octahedrite (6-7 mm). No obvious inclusions were noted. Terrestrial alteration appears to have only affected the exterior surface.

Geochemistry: ICP-MS data, using sample of North Chile (Filomena) as standard (C. Herd and G. Chen UAb): Ni = 5.9, Co = 0.47 (both wt%); Ir = 9.6, Ga = 48, As = 6.4, W = 2.4, Re = 0.8, Os = 1.0, Pt = 17.9, Cu = 101, Au = 0.9 (all µg/g).

Classification: IIAB iron, through comparison of bulk composition with data from Wasson et al. (2007), coarsest octahedrite. Composition is distinct from other known IIAB irons from Mexico, and this is the first known IIAB iron from Baja California.

Specimens: Type specimen consisting of 23 g in four slices at UAb. Main mass with the anonymous owner.

Nova 057: reclassification

Correction to Bulletin Entry for Nova 057 (C. Herd, UAb): A more precise INAA analysis, done shortly before his death by J.T. Wasson, UCLA, provides improved trace-element concentrations that place the meteorite in the IC iron field, and suggest the meteorite may be paired with Arispe, another IC iron from Mexico. Ni = 67.0, Co = 4.65 (both mg/g); Cr = 36, Cu = 120, Ga = 50.7, Ge = 211, As = 7.55, Ru = 13.6, W = 1.98, Re = 0.961, Os = 7.5, Ir = 9.87, Pt = 18.6, Au = 0.878 (all ug/g).

Nova 057: discredited

This specimen was originally described as a IIAB iron from Baja California, Mexico, with the exact find location unknown. There were no apparent pairings with other IIAB irons. However, it was recently reclassified as a member of the rare iron meteorite group IC. Based on reports supplied by Geoff Notkin through Chris Herd, it became evident that the iron was likely found in Sonora around 1955. This suggested a possible pairing with the large, multiple-mass, Arispe IC iron, also found in Sonora.

Petrography (C. Herd, UAb): The structure of Nova 057 is similar to Arispe. The bandwidth measured in a small section is 3.4±0.9 mm (n=5), similar to Arispe's 2.9±0.5 mm reported by Buchwald (1975). The presence of Neumann bands and cohenite "nests" is also similar to Arispe

Composition (J. Wasson and B. Zhang, UCLA): INAA analyses done of Nova 057 and Arispe are similar, and share the unique feature among IC irons of having a strong enrichment of refractory siderophiles such as Ir. These data are shown in the table below.

Based on this information, the name "Nova 057" is discredited as an official meteorite name. Henceforth, this specimen shall be known as the "Nova 057 mass of Arispe" and "Nova 057" becomes a synonym for Arispe

Element	Unit	Arispe	Nova 057
Cr	μg/g	79	36
Co	mg/g	4.67	4.65
Ni	mg/g	62.9	67
Cu	μg/g	118	120
Ga	μg/g	51.9	50.7
Ge	μg/g	246	211
As	μg/g	7.25	7.55
Mo	μg/g	7.4
Ru	μg/g	13.6
Rh	μg/g	1.9
Pd	μg/g	2.897
Sb	ng/g	99
W	μg/g	2.3	1.98
Re	ng/g	939	961
Os	μg/g	7.5
Ir	μg/g	10.07	9.87
Pt	μg/g	19.6	18.6
Au	μg/g	0.811	0.878