Northwest Africa 5351 (NWA 5351)

Erfoud, Morocco

Purchased: Dec 2007

Classification: HED achondrite (Eucrite, monomict)

History: The main mass holder purchased the sample in Tucson from a dealer who told him it was from Erfoud, Morocco.

Physical characteristics: Single, 139 g stone. Dark fusion crust with a rippled texture and shrinkage cracks covers one curved side. The remainder of the exterior consists of a weathered broken surface.

Petrography: (Melinda Hutson and Alex Ruzicka, Cascadia). In thin section, this meteorite shows relatively sharply defined, fine-grained basaltic clasts set in a fragmental matrix. The matrix material appears to be comprised of the same material as that found in the clasts. Clasts are mostly subophitic, although some are granular. Feldspathic material includes (1) twinned plagioclase which is either undeformed or which has weak undulose extinction, and (2) a clouded feldspathic phase that does not have the correct stoichiometry for feldspar, but which is not isotropic, so is not glass. No maskelynite was observed.

Geochemistry: (Melinda Hutson and Alex Ruzicka, Cascadia; Ilya Bindeman, UOr). EMPA analyses: Low-Ca pyroxene (Fs_62.6±0.7, Wo_2.5±0.6, n=21); "pigeonite" (Fs_50.5±7.3, Wo_15.4±7.6, n=11) which is probably a mixture of exsolved low-Ca pyroxene and augite; augite (Fs_26.6±0.2Wo_43.5±0.3, n=3); Fe/Mn ratios (all at%): low-Ca pyroxene Fe/Mn = 31.9 ± 1.4; augite Fe/Mn = 32.9±1.1; "pigeonite" (likely mixture) Fe/Mn = 31.4±1.1. Plagioclase (An_87.9±1.9Ab_11.7±1.8, n=22). Oxygen isotopes (whole rock): δ¹⁷O = -0.219±0.05 ‰, δ¹⁸O = 3.70±0.11 ‰

Classification: Achondrite (monomict eucrite). Minimal weathering and shock.

Specimens: 22 g and one thin section are on deposit at Cascadia. Thompson holds the main mass.