Northwest Africa 7921 (NWA 7921)

Morocco

Purchased: 2012

Classification: Carbonaceous chondrite (CV3)

History: Purchased by Brahim Tahiri from a Moroccan hunter and sent to his partner Sean Tutorow for classification, 2012.

Physical characteristics: Consists of 14 individual stones or fragments, several fit together. Dark irregular exterior, some weathered fusion crust, chondrules visible through desert patina, saw-cut reveals densely packed chondrules of variable size, many 1-2 mm, CAIs present.

Petrography: (C. Agee, UNM) Microprobe examination of a polished mount showed a sharp boundary between a large CAI and host matrix + chondrules. Matrix is very fine-grained with numerous porphyritic chondrules, accessory augite, diopside, aluminous diopside, and anorthite. Large CAI is approximately 95% gehlenite, with accessory spinel, hercynite-spinel, CaTiO3-perovskite, calcium carbonate, and Fe,Ni-metal.

Geochemistry: (C. Agee and L. Burkemper, UNM) Olivine range Fa_0.7-12.4, n=31, mean value ferroan olivine Fa_5.3±2.7, Fe/Mn=53±28, Cr₂O₃=0.09±0.07wt%, n=22; type I chondrule olivine Fa_1.2±0.3, n=9; low-Ca pyroxene range Fs_0.8-15.1, mean value Fs_2.6±3.1Wo_1.4±1.0, Fe/Mn=16±10, n=22. (Karen Ziegler, UNM) Oxygen isotope mean values of 3 analyses on 3 acid-washed aliquots of matrix + chondrules, 1.1, 1.1, 1.7 mg, gave δ¹⁷O= -4.671, -3.451, -5.223, δ¹⁸O= -0.661, +0.453, -0.306, Δ¹⁷O= -4.322, -3.690, -5.061 (all per mil).

Classification: Carbonceous chondrite (CV3), oxygen isotopes on CCAM, in CV3 field.

Specimens: 21.4 g including a probe mount on deposit at UNM, Sean Tutorow holds the main mass.