Northwest Africa 11299 (NWA 11299)

(Northwest Africa)

Purchased: 2017

Classification: Carbonaceous chondrite (CK5)

History: A single stone weighing 969.7 g was found in Morocco and subsequently purchased by Blaine Reed at the 2017 Tucson Gem and Mineral show.

Physical characteristics: The stone is dark-orangish-brown in color, has a flattened ovoid shape, lacks fusion crust and has a weathered exterior with some chondrules protruding through the surface. The cut face showing the interior of the stone is dark greenish-brown and shows readily discernible dark-colored chondrules and irregular to circular dark-gray metallic grains.

Petrography: Description and classification (A. Love, App): Sample is recrystallized and has a texture composed of distinct chondrules with an average diameter of 693 μm, chondrule fragments, irregularly shaped CAIs within a fine, transparent crystalline matrix. Olivine chondrules are dominant. Sample contains minor pyroxene, and plagioclase (<50 μm in length) and Cr-magnetite.

Geochemistry: Olivine: Fa_24.58±0.34 NiO 0.47±0.17, n=20; low Ca pyroxene Fs _21.29±0.67Wo_1.02±2.17, n=9; high Ca pyroxene Fs_4.77±3.11Wo_41.94±6.97, n=2; plagioclase Ab_65.01±7.67Or_5.93±0.23, n=8; magnetite= Cr₂O₃ 3.40±0.11wt%, Al₂O₃ 0.48±0.23wt%, NiO 0.1±0.07wt% (n=5).

Classification: CK5. CK based on dark coloring, presence of CAIs and ubiquitous Cr-magnetite. Petrologic type 5 based on textures and equilibrated mineral compositions. Specimen has low FeO compositions compared to more highly oxidized CK chondrites, but shares compositional similarities to: Graves Nunataks 98102 (CK4 Fa₂₄); NWA 5580 (CK4 Fa_25.2); NWA 7615 (CK6 Fa_24.7) and NWA 11207 (CK5 Fa_24.9).

Specimens: Two slices weighing 39.05 g and one polished thin section are on deposit at App. Blaine Reed holds the main mass.