Northwest Africa 8659 (NWA 8659)

(Northwest Africa)

Purchased: Oct 2013

Classification: HED achondrite (Eucrite)

History: The meteorite was found as a single mass of 45.8 g in 2013 by an anonymous searcher, and was purchased by A. Jonikas in Dec 2013.

Physical characteristics: The stone has a distinct dark crust, but this appears to be almost entirely desert varnish, not fusion crust.

Petrography: (P. Warren, UCLA) Slices through the stone indicate that most of the material is thoroughly brecciated, yet a single large clast comprising about 40% of the stone is essentially unbrecciated. The unbrecciated material shows a subopthitic texture with grain size typically 2 mm. Minor Fe-metal. The pyroxernes are to an unusual extent pervaded by secondary olivine-dominated veins.

Geochemistry: Pyroxene is mostly equilibrated to a tie-line between low-Ca pyroxene En_32.0±0.7Wo_3.4±0.4, FeO/MnO wt ratio 33.6±1.5, n=11, and high-Ca pyroxene En_26.6±0.1Wo_42.3±0.2, n=6, but in the cores of a few large grains a low-Ca zoning trend survives with composition as magnesian as En₅₈Wo₇; primary-igneous plagioclase An_81.3±2.4, n=40; secondary veins within pyroxenes have An₉₈ plagioclase, along with olivine Fa_83.5±0.5, n=11. Oxygen isotopes: (I. Kohl and E. Young, UCLA) δ¹⁷O 2.083, δ¹⁸O 4.376, Δ¹⁷O -0.227 (all normalized). Bulk composition: (fused-bead EPMA, in wt%, derived from a 0.28 g powder) SiO₂ 49.5, TiO₂ 1.28, Al₂O₃ 11.5, Cr₂O₃ 0.24, MgO 5.5, FeO 18.2, MnO 0.51; mg# 0.349.

Classification: Eucrite (monomict-brecciated). Unusually ferroan, Ti-rich, and rich in secondary metasomatic veins.

Specimens: The main mass, 34 g, is held by Aras Jonikas.