Ozerki        52°48.084’N, 38°10.268’E

Lipetskaya oblast’, Russia

Confirmed fall: 21 June 2018

Classification: Ordinary chondrite (L6)

History: The first meteorite fragments were recovered based on analysis of the fireball observed over the Lipetskaya oblast’ in Russia on June 21, 2018, at 01:16:20 UT. The fireball was widely observed from many places in Russia, including Moscow. The scientists from UrFU, UHelsinki, and the Finnish Fireball Network formed a consortium enabling quick prediction and the actual discovery of the meteorite. Collection of the observational data and trajectory analysis were done by Esko Lyytinen, Maria Gritsevich, Nikolai Kruglikov, and Mikhail Larionov. The derived parameters, characterizing the trajectory were clearly indicative of a number of  meteorite fragments landing on the ground. Using these results, a comprehensive model of the strewn field providing the expected locations of fragments was done by Jarmo Moilanen. The area of the meteorite shower was predicted to be on the line Ozerki – Zlobino - Druzhba, Stanovlyansky district, northwest of Yelets town, Lipetskaya oblast’. The modeling assumed about 100 meteorites (excepting the main body) with total mass ~7 kg. With the support of these data, a meteorite recovery campaign was initiated by Victor I. Grokhovsky. Five samples of the meteorite (1176 g) were recovered during the UrFU meteorite expedition-2018 (23-27 June 2018; Pastukhovich A.Yu., Yakovlev G.A., Petrova E.V. and volunteer Usenkov A.V.) in the Lipetskaya oblast’. The first sample was found 25 June 2018 by G.A. Yakovlev (59.85 g). The UrFU finds were near Ozerki village. During the next few weeks, more meteorite samples (>5500 g) were recovered by institutional groups (Vernad - GEOKHI RAS, IA RAS, IDG RAS) and private collectors in the area Ozerki – Zlobino. The total mass and number of stones may increase due to additional finds.

Physical characteristics: The meteorites have roughly rounded shapes, covered by dark fusion crust; the interior is light colored and contains visible opaque shock veins. The samples are fresh, but halos of Fe-hydroxides were already present around metal grains. Some samples contain impact melt.

Petrography: (V.V. Sharygin, SIGM and UrFU, and D.A. Zamyatin, RAS-UB and UrFU): Petrographic observation of a polished section shows very rare chondrules in a coarse recrystallized matrix. Most chondrules are very poorly defined and their apparent sizes vary from 200 µm to 1 mm. Only the largest chondrules (up to 4 mm) are clearly delineated. The PO, POP and BO chondrules are most common and mainly consist of olivine, plagioclase, low-Ca pyroxene ± chromite and blebs of troilite and FeNi-metal. Other textural types of chondrules were not observed. Olivine, low-Ca-pyroxene, plagioclase, FeNi-metal and troilite are the main minerals in the matrix. Clinopyroxene, chromite, chlorapatite and merrillite (100-300 µm) occur locally in the matrix. Plagioclase grains are larger than 50-100 µm. Shock features include undulatory extinction, irregular and planar fractures (three directions) in olivine and the presence of opaque shock veins. The presence of impact melt suggests shock stage S5. Grains of FeNi metal (up to 1 mm) are represented by both individual phases (kamacite, taenite or plessite) and their intergrowths (kamacite + taenite, kamacite + plessite + tetrataenite, kamacite + tetrataenite + pentlandite) ± troilite. Grains of troilite (100-500 µm) are spongy, fine-grained aggregates of micrometer-sized individuals (<5 µm). Some pentlandite grains occur in such aggregates, especially on contacts with FeNi-metal. Opaque shock veins (up to 100 µm in thick) are not very abundant and contain metal-sulfide intergrowths in fine-grained low-Ca pyroxene matrix. The thickness of fusion crust is up to 600 µm. It is highly vesicular and zoned in texture: the outmost zone is a cryptocrystalline aggregate of skeletal crystals of zoned olivine and magnetite (up to 5 µm) and glass (44-47 wt.% SiO₂); the inner zone is represented by larger skeletal crystals of newly formed olivine + glass + minor magnetite. Both zones contain rounded relics of initial olivine and chromite and newly formed Ni-rich metal-sulfide globules (10-20 µm). Magnetic susceptibility log χ (× 10^-9 m³/kg) = 4.8 (analyst Yakovlev G.A.).

Geochemistry: SEM-EDS-WDS (V. V. Sharygin, SIGM and UrFU) and EMPA-WDS (D.A. Zamyatin, RAS-UB and UrFU). Olivine Fa_25.6±0.3 (N=51), low-Ca pyroxene Fs_21.4±0.2Wo_1.6±0.3 (N=44), plagioclase Ab_83.5An_10.5Or_6.0 (N=35), Cr-bearing clinopyroxene En_45.8Fs_9.0Wo_45.2 (Cr₂O₃ – 0.8-1.0 wt.%, N=6), chromite Crt_82.8Spl_12.1 (N=17), chlorapatite, merrillite, FeNi-metals, troilite and pentlandite. Chlorapatite contains F (up to 0.5 wt.%); Cl – 5.5, Na₂O – 0.5 wt.% (N=11). Merrillite is poor in FeO (0.3-0.7 wt.%, N=8). Composition of metal (in wt.%): kamacite (N=32) – Fe 93.2±1.4, Ni – 5.89±1.44, Co – 0.92±0.13; taenite (N=20) – Fe 68.6±5.1, Ni 31.0±5.1, Co 0.36±0.09; tetrataenite (N=3) – Fe 48.5, Ni 51.2, Co 0.16. Composition of sulfides (in wt.%): pentlandite (N=10, in association with troilite) – Fe 50.6±0.8, Ni 15.4±1.0, Co 0.15±0.02, Cu 0.61±0.26, S 33.6±0.3; heazlewoodite (N=10, from fusion crust) – Fe 2.62±0.46, Ni 71.4±0.8, Co 0.11±0.01, Cu 0.37±0.09, S 25.6±0.5.

Classification: Ordinary chondrite. L6, S5, W0.

Specimens: UrFU - 798.6 g (3 samples: 550.4, 188.3, 59.9 g); Vernad - 603 g (3 samples); SIGM - 31.7 g fragment; RAS-UB - 15 g fragment; UHelsinki - 15 g fragment.