Northwest Africa 6259 (NWA 6259)

(Northwest Africa)

Find: 2010 Feb

Classification: Iron meteorite (ungrouped)

Petrography: Petrographic description. Sample is neither well polished nor etched. Based on this sample, the structure is that of a Ni-rich ataxite. The only recognized inclusions are small troilite ovals with lengths in the range 2 to 6 mm and widths typically 2/3 of the length. A layer of dark oxide, probably a weathering product, surrounds these FeS blebs. The surface is heavily oxidized but the sawed and roughly polished faces oxidize only slowly in the storage container.

Geochemistry: Composition (based on duplicate INAA): Co, 6.08 mg/g; Ni, 422 mg/g; Cu, 3250 μg/g; Ga, 5.76 μg/g; As, 39.5 μg/g; Sb, 4595 ng/g; W, 0.15 μg/g; Ir 0.027 μg/g; Au, 3.40 μg/g. The meteorite has an extraordinary composition. The Sb content is the second highest known, second only to Oktibbeha County.

Classification: The meteorite is ungrouped with no close relatives. Because of the high As, Au, Sb and Cu it may be related to the IAB complex.