Northwest Africa 15175 (NWA 15175)
Classification: Carbonaceous chondrite (CR2)
History: Found in 2021 in Algeria, in the Erg Chech area. Bought by Isabelle Pothier in Morocco.
Physical characteristics: Dark stone. Cut face reveals large well-delineated chondrules and metal.
Petrography: (J. Gattacceca, CEREGE; Trygve Prestgard, IPAG) Chondrite with well-delineated chondrules with apparent diameter 1160±410 µm (n=14) and CAIs (<1 vol.%) up to 3 mm in diameter set in an abundant fine-grained iron-rich matrix. Opaque minerals are troilite, metal (6.1 vol.%), and magnetite.
Geochemistry: Olivine Fa1.4±0.2, range Fa1.1-1.7 (n=6). Low-Ca pyroxene Fs1.6Wo0.7 (n=2). Defocused analyses of the matrix FeO 29.4 wt%, analytical total 85.1 wt% (n=2). Clast: olivine Fa 2.7 (n=1), defocused matrix FeO 31.0±1.0 wt% and analytical total 79.4±3.7 wt% (n=4). IR spectra of the matrix (Trygve Prestgard, IPAG) show widespread Fe-rich hydrated silicates, scarce and barely detectable carbonate signature, and presence of olivine in all matrix fragments.
Classification: Carbonaceous chondrite (CR2). The low analytical totals in the matrix and IR transmission transmission spectroscopy indicate the presence of hydrous phases. Based on IR spectroscopy, the extent of aqueous alteration is likely lower than that of Renazzo.
Specimens: Type specimen at CEREGE. Main mass with Isabelle Pothier.
Mass (g): 309
Pieces: several
Class: CR2
Weathering grade: low
Classifier: J. Gattacceca (CEREGE), T. Prestgard (IPAG)
Main mass: Isabelle Pothier
