Shinejinst        44°37’15.6"N, 99°012’38.1"E

Bayankhongor, Mongolia

Find: 2018 Aug 30

Classification: Ordinary chondrite (H4)

History: Four fragments (156.17, 101.73, 208.17, and 227.35 g) were found on 30 and 31 August 2018 by the UrFU - IAG-MAS meteorite expedition-2018 in Southern Gobi (Pastukhovich A.Yu., Kolunin R.N., Larionov M.Yu., Muraviev L.A., Petrova E.V., Yakovlev G.A., Naasa Ochir) 10 km northwest of Shinejinst, Bayankhongor aimag (province), Mongolia.

Petrography: Classification (K. Dugushkina and S. Berzin, RAS-UB). Petrographic observation of a polished section shows a fine-grained inequigranular recrystallized matrix and chondrules (25%). Chondrite consists of olivine 50%, orthopyroxene 15%, clinopyroxene 10%, plagioclase 15%, chromite 3%, troilite 3-4%, Fe-Ni-metal 3-4%. Also chondrite contains accessory apatite and ilmenite. Predominate porphyritic olivine (PO) and porphyritic olivine-pyroxene (POP) chondrules. Chondrules mostly have even boundaries. Petrographic type is 4. Chromite-plagioclase assemblages are found in the recrystallized matrix. The assemblages range in size from 10-350 µm and consist of 0.2-30- µm-size rounded, euhedral, subhedral and anhedral chromite grains surrounded by plagioclase or glass of plagioclase composition. Moderate oxidation of metal, about 20-60% being affected, alteration of mafic silicates is beginning (weathering grade - W2). The samples are transected by dark shock veins. Shock stage is S3/4.

Geochemistry: EDX analyses by K. Dugushkina, RAS-UB. The meteorite is composed olivine Fa_20±2.1 (N=37), low-Ca pyroxene Fs_18±0.4En_80±0.4Wo_1±0.3 (N=17), plagioclase An_24±3.5 (N=9), clinopyroxene En_49±3.6Fs_10±1.7Wo_42±2.8 (N=6), chromite, troilite, kamacite (Ni 5.5-6.8 wt%), taenite (Ni 19.7-36 wt%), apatite and ilmenite. Average composition of chromite (N=9): Cr₂O₃ 55.6±0.9 wt%, FeO 28.4±1.4 wt%, MgO 4.8±1.1 wt%, Al₂O₃ 7.8±0.8 wt%, TiO₂ 2.2±0.2 wt%, MnO 0.7±0.04 wt%, SiO₂ 0.5±0.17 wt%, CaO 0.1±0.02 wt%, NiO 0.2±0.01 wt%.

Classification: Ordinary chondrite (H4)

Specimens: 591 g (3 samples) at IAG-MAS; 96.43 g sample and 5.30 g cut-off and thin section at UrFU.