Northwest Africa 10851 (NWA 10851)

(Northwest Africa)

Purchased: 2002 Jan

Classification: Primitive achondrite (Winonaite)

History: (I. Nicklin, ROM) Dr. David Gregory donated a lot of 345 meteorites to ROM in 2009. The pieces ranged in size from 14 × 11 × 8.5 cm to less than 1 × 1 × 1 cm, with an aggregate weight of 57.2 kg. These had been purchased from Dean Bessey in 2002 as NWA 869 material, acquired in Morocco. Based upon visual inspection of each piece, it was apparent that 18 of the specimens are unlike the predominant NWA 869 pieces, and most of these have subsequently been identified as other types of ordinary chondrites (e.g. H4 NWA 6998). However, the stone designated as M48964 and described here was clearly different.

Petrography: (A. Irving and S. Kuehner, UWS) Breccia composed of clasts exhibiting triple grain junction textures within a coarse grained matrix exhibiting similar texture. The grainsize in individual clasts varies and ranges from 0.1 mm to 0.2 mm. Minerals are predominantly enstatite with accessory forsterite, stained Ni-poor kamacite, schreibersite, daubreelite, troilite and pentlandite.

Geochemistry: Enstatite (Fs_0.4-0.5Wo_0.6-0.7, N = 3), forsterite (Fa_0.2-0.3, N = 2). Oxygen isotopes (K. Ziegler, UNM): analysis of acid-washed subsamples by laser fluorination gave, respectively, δ¹⁷O 2.345, 2.149, 2.224; δ¹⁸O 5.438, 5.078, 5.242; Δ¹⁷O -0.526, -0.532, -0.544 per mil.

Classification: Winonaite (breccia).

Specimens: 8.18 g including one polished thin section at ROM; remainder with DGregory.