Northwest Africa 14589 (NWA 14589)

(Northwest Africa)

Purchased: 2021 Jul

Classification: Ungrouped achondrite

History: Purchased by Matthew Stream in July 2021 from an Algerian dealer.

Petrography: (A. Irving, UWS and J. Boesenberg, BrownU) Breccia composed predominantly (>90 vol.%) of deformed magnesian olivine grains (up to 1.7 cm in size) together with much smaller angular grains of orthopyroxene, diopside, calcic plagioclase, pigeonite (containing ~10 µm diopside inclusions), chromite (with variable Fe/Mg and Al/Cr ratios), pentlandite, troilite, merrillite and stained Fe metal. Olivine grains exhibit multiple internal tilt boundaries, and contain abundant inclusions of troilite, Fe metal and chromite.

Geochemistry: Olivine (Fa_11.7-16.3, FeO/MnO = 40-43, N = 11), orthopyroxene (Fs_14.2-14.7Wo_3.1-4.6, FeO/MnO = 22-25, N = 9), pigeonite (Fs_12.6Wo_12.9, FeO/MnO = 22), diopside (Fs_7.5-7.7Wo_40.7-40.6, FeO/MnO = 17-18, N = 2), plagioclase (An_86.7-92.9Or_0.8-0.2, N = 6).

Classification: Ungrouped achondrite (dunitic breccia, magnesian). Although the mafic silicates in this specimen have FeO/MnO ratios in the ranges for diogenites and mesosiderites, they are much more magnesian than the corresponding phases in those achondrites. This specimen bears some textural and mineralogical resemblance to ungrouped olivine-rich breccias NWA 12217, NWA 12319 and NWA 12562 (Vaci et al., 2021), but in detail there are differences (notably the much more calcic plagioclase in this specimen), so pairing with any of those specimens is excluded.

Specimens: 23.6 g including one polished thin section at UWB; remainder with Mr. M. Stream.