Northwest Africa 13334 (NWA 13334)

Northwest Africa

Purchased: 2009

Classification: Ureilite

Physical characteristics: Found as 109 small stones; coarse-grained, dark, with weathered, vein-like, interstitial materials.

Petrography: A somewhat coarse-grained but otherwise typical ureilite texture and mode, mostly olivine but roughly 1/4 pigeonite. Granular yet curvy-bounded silicate grains are up to 6 mm across, but 2 mm is more typical. Tiny metals are present in reduced rims within olivine. Minor vein-like interstitial matter is weathered, largely opaque (carbon-rich, probably).

Geochemistry: Mineral compositions and geochemistry: The olivine cores are Fa_18.8±0.1 (6 analyses), but rims are as Fe-poor as Fa_2.1. Minor elements in the olivine cores average 0.62±0.06 wt% Cr₂O₃, 0.36±0.08 wt% MnO, and 0.31±0.05 wt% CaO. The pyroxene is a pigeonite, Fs_16.3Wo_6.3, with no analytically significant range for major elements among 6 analyses. Minor elements in the pigeonite average 1.14±0.02 wt% Cr₂O₃, 0.90±0.03 Al₂O₃, and 0.41±0.06 wt% MnO.

Classification: Ureilite

Specimens: a type specimen, 24.1 g, is at UCLA; also 24.9 g is at UBayr. Main mass: Sean Tutorow (Tutorow’s web site: www.eegooblago.com; Tutorow’s email: [email protected]).