Uakit        55°29’47.50"N, 113°33’47.98"E

Respublika Buryatiya, Russia

Find: summer 2016

Classification: Iron meteorite (IIAB)

History: The meteorite was found in the summer of 2015 by a gold prospector group during excavation on a river terrace (stream Mukhtunnyi, left feeder of the Uakit River) 4 km west of the Uakit settlement (Baunt Evenk district, Respublika Buryatiya). At present, one sample (~4 kg) of meteorite was identified. However, information about the discovery of a larger meteorite mass (~50x50 cm) is known among prospectors around Uakit. The date of fall is unknown.

Physical characteristics: The 3.96 kg mass is oval (10 × 10 × 7 cm) with brown to yellow-brown exterior.

Petrography: Classification (G.S. Ripp, GI-SBRAS, Victor V. Sharygin, SIGM). Polished and then etched surfaces indicate large (~2 cm) kamacite crystals and show no Widmannstatten pattern; Neumann lines are evident. Weathering and fusion crusts are less than 1 mm thick. Sometimes they extend together along some fractures, but their abundance is low. The meteorite contains kamacite (>98 vol.%), schreibersite (rhabdite), nickelphosphide, taenite, cohenite, daubreelite, kalininite, troilite, carlsbergite, sphalerite, phase VN, cooper, awaruite-nickel, Ni-rich magnetite, pentlandite, heazlewoodite, Ni-rich goethite and other Fe-hydroxides (sometimes with Cl). Cohenite occurs locally (near exterior) and forms crystals up to 0.5 mm. Ni-poorer taenite (<33 wt% Ni), Ni-rich kamacite (>6.3 wt% Ni) and nickel phosphide are most common of the cohenite-containing associations. Schreibersite (20-100 μm) and carlsbergite (1-10 μm) crystals are commonly oriented in one direction in the kamacite matrix. Round isolations (up to 100 μm) of daubreelite (± troilite ± VN ± copper) occur rarely. Magnetite, pentlandite, awaruite-nickel and heazlewoodite are related to the fusion crust, whereas goethite and other Fe-hydroxides are weathering products.

Geochemistry: Mineral composition and Geochemistry: Chemistry of the main metals (EMPA-WDS analyses, V.V. Sharygin and E.N. Nigmatulina, SIGM): kamacite (N=25; Fe = 93.38±0.56; Ni = 6.18±0.48; Co = 0.49±0.05); taenite (N=13; Fe = 68.19±6.62; Ni = 31.62±6.79; Co = 0.14±0.05); cohenite (N=14; Fe = 91.60±0.31; Ni = 1.59±0.05; Co = 0.07±0.02, all in wt%). Geochemistry for kamacite (LA-ICP-MS data using sample of Sikhote-Alin as a standard, 50 µm beam, A.L. Ragozin, SIGM - NSU and V.V. Sharygin, SIGM): N=13; Cr = 15-138; Cu = 144-191; V = 0.04-0.52; Zn = 5.0-29.8; Ga = 46-58; Ge = 188-233; As = 4.1-6.1; Mo = 1.7-6.0; Ru = 5.1-18; Rh = 1.6-2.4; Pd = 2.0-2.8; In = 0.003-0.009; Sb = 0.001-0.054; W = 1.6-2.6; Re = 1.4-2.0; Ir =10.3-22.7; Pt = 21.2-33.4; Au = 0.48-0.70 (all in µg/g). Bulk composition of the meteorite (solution ICP-MS data using sample of Sikhote-Alin as a standard, I.V. Nikolaeva, S.V. Palessky and O.A. Kozmenko, SIGM): N=2; Ni = 5.47; Co = 0.45 (both in wt%); Si =732-886; P = 989-1063; Cr = 127-139; Cu = 149-294; V = 0.10-0.24; Zn = 6-68; Ga = 49-50; Ge = 203-215; As = 2.4-3.0; Mo = 5.1-5.9; Ru = 18.7; Rh = 2.0; Pd = 1.26-1.40; Sn = 6.9-44; Sb = 0.064-0.10; W = 3.0; Re = 1.67-1.76; Ir <20; Pt = 24; Au = 0.51-0.53 (all in µg/g). The broad variations for some elements in kamacite and bulk are evidenced about their heterogeneous distribution in the meteorite, may be due to local abundance of minor and accessory minerals (cohenite, daubreelite, kalininite, carlsbergite, sphalerite, etc.).

Classification: (G.S. Ripp, GI-SBRAS, Victor V. Sharygin, SIGM). Iron, IIAB (with tendency to IIA)

Specimens: 70.3 g type specimen (SIGM), 18 g cut-off fragments (Mineralogical Museum at B G I), main mass (O.Yu. Korshunov, V.O. Korshunov, Ulan-Ude)