Northwest Africa 7317 (NWA 7317)

Northwest Africa

Purchased: 2012

Classification: CR6

History: Purchased by Marcin Cimała and Tomek Jakubowski from two separate dealers in Erfoud and Zagora in 2012 April and June.

Physical characteristics: Four fresh, pale greenish stones (122 g, 151 g, 187 g, 636 g), all partially coated with black fusion crust.

Petrography: (A. Irving and S. Kuehner, UWS) Overall poikiloblastic texture, but there are rare BO chondrules with annular olivine rims. Minerals present include olivine (some as larger grains), orthopyroxene, minor clinopyroxene, intermediate plagioclase, fresh kamacite, chromite, troilite, and merrillite.

Geochemistry: Olivine (Fa_38.0-38.2, FeO/MnO = 72-79), orthopyroxene (Fs_29.3-29.4Wo_3.3-3.0, FeO/MnO = 53-61), clinopyroxene (Fs_12.8-14.2Wo_42.7-40.5, FeO/MnO = 40-41). Oxygen isotopes (R. Tanaka, OkaU): analyses of acid-washed subsamples by laser fluorination gave δ¹⁷O = 0.057, 0.064; δ¹⁸O = 3.507, 3.594; Δ¹⁷O = -1.788, -1.827 per mil.

Classification: Carbonaceous chondrite (CR6). This specimen is a highly equilibrated CR chondrite paired with NWA 2994, NWA 3250, NWA 6901 and NWA 6921.

Specimens: A total of 22 g of sample and one polished thin section are on deposit at UWB. Mr. M. Cimała and Mr. T. Jakubowski jointly hold the main masses.