Northwest Africa 10310 (NWA 10310)

(Northwest Africa)

Purchased: April 2013

Classification: Ordinary chondrite (L6)

History: Purchased on-line as an NWA meteorite originally from a Moroccan dealer by John Shea in April 2013 and a portion subsequently donated to Cascadia.

Physical characteristics: Already cut individual with partial fusion crust. Sawed faces show chondritic texture with rust haloes around the metal.

Petrography: (M. Ream and A. Ruzicka, Cascadia) Large chondrules in this sample are somewhat readily recognized in thin section with transmitted light, but boundaries are indistinct and matrix is mostly transparent, and feldspar grain size is up to 100 μm across, consistent with petrographic type 6. The mean diameter of the recognizable chondrules (N = 20) is 0.9±0.4 mm. Contains about 4% metal + 6% troilite (+ minor weathering products). Olivine grains are mosaicized and most grains display 2 sets of planar fractures indicative of shock stage S4. Chromite-feldspar pods are also present. One unusual ~3-mm- diameter object is concentrically zoned with a fine-grained (10 – 30 μm) core of silica and metal, a mantle of low- and high-Ca pyroxene, and a ragged, 50 – 100 μm thick rim of feldspar ± chromite with 5 – 10 μm grains of troilite dispersed evenly throughout the object.

Geochemistry: Olivine, Fa _25.8±0.4(Fa_25.4-26.8, N = 12); low-Ca pyroxene, Fs_21.6±0.4Wo_1.8±0.3 (Fs_21.1-22.5, N = 9); high-Ca pyroxene, Fs_8.6±2.2Wo _45.2±2.5 (Wo_43.4-46.9, N = 2); feldspar, Ab_84.8±4.2Or_5.9±1.4 (Ab_81.8-91.1, N = 4).

Classification: Data are most consistent with an L6 chondrite.

Specimens: Cascadia holds 40.4 g, a polished thin section, and potted butt. John Shea holds the main mass.