Northwest Africa 12923 (NWA 12923)

Niger

Purchased: 2017

Classification: Ordinary chondrite (H5, melt breccia)

History: Wang Chen and Ziyao Wang purchased many individual specimens totaling 3.4 kg and 2 kg respectively from a Moroccan meteorite dealer during the 2017 Beijing International Mineral, Gem & Fossil Show.

Petrography: (C. Herd, UAb) Examination of two ~2 × 4 cm sequential slices and a ~1.5 × 2.5 cm slice (later used to make the thin section) shows dark-gray rounded clasts containing metal and silicates with some microporosity, surrounded by lighter-gray microcrystalline domains which often have vein-like morphology relative to the clasts. Metal grains in the clasts are mostly <0.5 mm, but locally up to 5 mm in longest dimension. At thin section scale, the clasts consist of poorly-delineated chondrules, metal and sulfides in a typical equilibrated ordinary chondrite texture. Microcrystalline domains are glassy in places under optical microscopy. Under the electron microprobe, these domains consist of ~150 μm scale rounded sulfide blebs, and clasts of olivine and low-Ca pyroxene set in a fine-grained matrix of olivine and feldspathic glass; these are likely shock melt veins. Other shock effects include strong mosaicism in olivine.

Geochemistry: (C. Herd and L. Tunney, UAb) Data obtained by EMP examination of carbon-coated thin section: Clast Olivine Fa_{18.7 ± 0.3} (n=10); vein olivine Fa_18.3±0.1 (n=3). Low-Ca Pyroxene in clasts Fs_16.4±0.4, Wo_1.7±0.1 (n=9); vein pyroxene Fs_16.1, Wo_1.7 (n=1). Clast Feldspar Or_3.1Ab₇₅ (n=1).

Classification: Ordinary chondrite, H5-melt breccia. Likely paired with Tassedet 004.

Specimens: Type specimen of 21.1 g, including one thin section, at UAb. Many stones totaling 3.4 kg with Wang Chen, 2 kg with Ziyao Wang.