Northwest Africa 11176 (NWA 11176)

(Northwest Africa)

Purchased: 2015

Classification: Ordinary chondrite (LL5)

History: A 114.6 g meteorite was acquired from a Moroccan meteorite dealer at the 2015 Tucson Gem and Mineral show.

Physical characteristics: Angular stone, one side shows well-developed fusion crust. The sawn surface is light colored with patches of iron-oxide staining. Even distribution of metal grains approximately 0.5-mm in size, troilite grains most approximately 1 mm in size, with some to 3 mm, and well developed chondrules, with average diamieter of 1.16 mm based on measurements of 32 chondrules. Metal and troilite are sparse at approximately one aerial percent of the sample.

Petrography: (J. Barkl, L. Garvie ASU) Range of chondrule types visible in the thin section, including radial olivine, RP, BO, PO, and CC; several in the 3 to 4 mm size range. Matrix fine-grained and recrystallized with abundant feldspar to 50 μm. Accessory angular and fractured chromite to 150 μm. Rare tetrataenite grain to 150 μm. Troilite typically polycrystalline and occasionally twined. Kamacite frequently rimmed by tetrataenite showing weakly developed Newman bands. Kamacite shows only minor weathering.

Geochemistry: (A. Wittmann, J. Barkl, L. Garvie ASU) Olivine Fa_30.1±0.8, FeO/MnO = 61.6±7.8, n=10; Low Ca-pyroxene Fs_25.2±1.7Wo_1.8±0.1, FeO/MnO=37.4±6.9, n=4. Plagioclase An_12.6±0.6Or_5.9±1.1, n = 3. Two kamacite analyses: Ni 4.8 at%, Co 3.3 at%; and, Ni 3.8 at%, Co 3.6 at%. Taenite, Ni 35.8±2.6 at%, Co 1.7 at%, n=10.

Classification: Ordinary chondrite (LL5), S3, W2.