NORTHWEST AFRICA 12758


Achondrite, ungrouped
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Purchased Jan 2019
no coordinates recorded

A single relatively unweathered stone meteorite weighing 2,400 g was found in Northwest Africa, with the country given as Mali. The meteorite was subsequently purchased by A. Habibi from a dealer in Agadir, Morocco. A sample was sent for analysis and classification to the University of Washington in Seattle (A. Irving and S. Kuehner) and Washington University in St. Louis (P. Carpenter), including an oxygen isotope analysis at the University of New Mexico (K. Ziegler), and NWA 12758 was classified as an ungrouped achondrite.

Northwest Africa 12758 is described in the MetBull write-up (#108) as a protogranular aggregate composed of low-Ca pyroxene (~70 vol%) and magnesian olivine (~30 vol%; Fa6.5–6.9; FeO/MnO = 29–39), together with accessory Si-bearing kamacite and Cr-bearing troilite. No plagioclase was observed in the analysis. The oxygen three-isotope plot falls along the CR chondrite trend. Another group of achondrites which plot long the CR O-isotopic trend line are the ténéréites (Agee et al. (2020). However, that group has very different mineralogy (e.g., they contain plagioclase) and chemistry (Fa~29–47; FeO/MnO = 66–94), which rules out a genetic relationship.

The specimen of NWA 12758 shown above is a 2.19 g partial slice. The photos below better exhibit the full-scale details of this unique achondrite, shown courtesy of Aziz Habibi.

Main Mass of NWA 12758
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Close-up View of NWA 12758
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Photos courtesy of Aziz Habibi