Northwest Africa 2625

Northwest Africa

Purchased 2004 August

Achondrite (ureilite)

A 305 g single stone was purchased in Erfoud, Morocco. Description and classification (J. Wittke and T. Bunch, NAU): medium- to coarse-grained (<4 mm), typical ureilite with pronounced preferred orientation of silicates, which are mostly elongated with curvilinear morphology. Pigeonite shows well-defined twinning; graphite and carbonaceous-metal-silicate-masses tend to cross trend the lineation direction with some small masses poikilitically enclosed by large pigeonite. The degree of olivine–pigeonite reduction is low to moderate. Olivine cores, Fa_20.3 (Cr₂O₃ = 0.72 wt. %), rims are Fa_8-10.8 (Cr₂O₃ = 0.53 wt. %); pigeonite, Fs_17.4Wo_7.6 (Cr₂O₃ up to 1.56 wt. %). Weathering is low grade and the shock level is S2. Specimens: type specimen, 22.2 g, NAU; main mass, GHupé.