Northwest Africa 6475 (NWA 6475)

Morocco

Purchased: 2010 Sep

Classification: HED achondrite (Eucrite, polymict)

History: Material from one large and 13 additional smaller stones were purchased in September 2010 by Marc Jost from a dealer in Semara, southern Morocco.

Physical characteristics: Fourteen stones totaling 602 g of a fragmental breccia containing angular gray, white, black and sparse metal clasts.

Petrography: (A. Irving and S. Kuehner, UWS) Polymict breccia composed mostly of basaltic and cumulate eucrite clasts (some partly recrystallized) and related debris, dark carbonaceous chondrite clasts and sparse angular clasts of metal (up to 8 mm across, with narrow oxidized rims). Diogenite clasts and diogenitic orthopyroxene appear to be absent. Minerals include exsolved pigeonite (clinopyroxene lamellae within orthopyroxene host, and vice versa), unexsolved pigeonite, calcic plagioclase, silica polymorph, ilmenite, chromite and troilite. Metal clasts consist of kamacite with some enclosed taenite. Chondrite clasts (CM2) consist of dispersed dust-rimmed magnesian chondrules and more ferroan olivine fragments in a dark matrix containing intergrown cronstedtite-tochilinite, pentlandite, Cr-Fe-Ni-phosphosulfide, djerfisherite and calcite (apparently primary), as well as sparse small, rimmed CAI composed predominantly of spinel and perovskite.

Geochemistry: Orthopyroxene (Fs_60.7-62.3Wo_1.8-1.6; FeO/MnO = 32), clinopyroxene exsolution lamellae (Fs_25.6-29.0Wo_44.0-41.4; FeO/MnO = 31-33), pigeonite (Fs_23.6Wo_11.8; FeO/MnO = 30), olivine in chondrite clasts (Fa_1.1 and Fa_61.7), enstatite in chondrite clasts (Fs_1.1Wo_2.0; FeO/MnO = 40).

Classification: Achondrite (eucrite, polymict).

Specimens: A total of 20.7 g of type material, one large polished thin section and a serial polished thick section are on deposit at UWS. The remaining material is held by Mr. M. Jost.