||North West Africa
||Polished thin section
Image NWA 2968 1
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History and physical characteristics: A bag of rectangular to blocky, dark brown meteorite
fragments, with a total mass of 268 g and collected by nomads in 2004, was purchased in
Erfoud, Morocco, in November 2005.
Petrography: (T. Bunch and J. Wittke, NAU; A. Irving, UWS) A massive olivine-rich rock of very
large grain size (17 to >25 mm; maximum size is unknown because of the tendency to fracture
on cutting). Curved to linear compression and shear fractures are subparallel to one of the
extinction directions in olivine and are responsible for the common rectangular/blocky habit.
Twenty-three pieces (1.8 to 20.1 g) were surveyed. Olivine accounts for >95 vol% with small
amounts of tiny grains (<0.03 mm) of orthopyroxene, metal, troilite, and pyrrhotite commonly
found within fractures and as rare inclusions in olivine. Large domain offset, isolated
mosaicism, and undulatory extinction are prevalent in olivine.
Mineral compositions and geochemistry: Equilibrated olivine (Fa7.5±0.2; FeO/MnO = 48;
Cr2O3 and NiO < 0.03 wt%), orthopyroxene (Fs6.7Wo1.5; FeO/MnO = 26), kamacite (Ni = 4.7–
6.8 wt%), taenite (Ni = 39.1–50.7 wt%), troilite (Ni = 0.36 wt%), pyrrhotite (Ni = 1.7–4.7 wt%).
Oxygen isotopes: (D. Rumble, CIW) Analysis of two cleaned and metal-free samples by laser
fluorination yielded δ17O = 1.44, 1.46; δ18O = 3.08, 3.64 and Δ17O = −0.178, −0.212 (all ‰).
Classification: Achondrite (ungrouped).
Type specimen: A 22 g sample is on deposit at NAU. Reed holds the main mass.
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