Kerman 255        30°45.477’N, 57°48.085’E

Kerman, Iran

Find: 2017 Jan 9

Classification: Ordinary chondrite (H5)

History: Meteorite (3 samples, 35.3 g) was found 9 January 2017 by the UrFU meteorite expedition-2017 in Iran (Pastukhovich A.Yu., Larionov M.Yu., Kruglikov N.A., Zamyatin D.A.) in the northwest part of the Kalout region of the Lut desert. All fragments of the meteorite were observed on the hard surface (probably, the place of fall).

Physical characteristics: Total mass is 35.3 g. All fragments have angular to roughly rounded shape. The surface and interior of the meteorite is light to dark brown in color due to abundant Fe-hydroxides. Some parts have glassy-like surface due to desert weathering. Some small cracks are totally filled with Fe-hydroxides and sulfates.

Petrography: Classification (Victor V. Sharygin, SIGM and UrFU). Petrographic observation of a polished section shows chondrules in a recrystallized matrix. Chondrules are readily delineated and their sizes mostly vary from 600 to 1000 µm. They have PO, POP and RP texture and some of them consist of Ol+Opx+Cpx+Pl±Crt or Ol+Opx+Pl±Crt. Olivine, low-Ca-pyroxene and plagioclase are main minerals in middle-grained matrix. Plagioclase grains are less than 50 µm. This indicates a petrologic type of 5 for the meteorite. Undulatory extinction and irregular fractures in olivine, as well as the absence of opaque shock veins and melt pockets, indicate a shock stage of S2. Grains of FeNi metals (kamacite, taenite, tetrataenite, up to 300 µm) and troilite (up to 250 µm) are partially altered. Weathering products (goethite, "hydrogoethite", akaganeite and other Fe-hydroxides, rarely anhydrite and magnetite) occur as veins and in situ alteration of FeNi-metals and troilite and fill all microfractures in minerals from matrix and chondrules (weathering grade – W2). Clinopyroxene, chromite, chlorapatite and merrillite (up to 300 µm) occur locally in the matrix. Pyrrhotite and hydrated sulfide FeS•nH₂O (alteration after troilite?) form grains up to 100-200 µm.

Geochemistry: EDS-WDS analyses (Victor V. Sharygin, SIGM and UrFU). The primary chondrite paragenesis includes olivine Fa_19.68±0.20 (N=42), low-Ca-pyroxene Fs_17.03±0.23Wo_1.42±0.22 (N=31), plagioclase Ab_82.8An_11.1Or_6.1 (N=11), Cr-bearing clinopyroxene En_46.6Fs_7.7Wo_45.7 (Cr₂O₃ – 0.8 wt.%, N=5), chromite Crt_80.9Spl_13.9 (N=7), chlorapatite, merrillite, FeNi-metals and troilite. Chlorapatite contains F (0.8-1.1 wt.%) and Cl (4.5-4.9 wt.%, N=2). Merrillite is poor in FeO (0.5-1.8 wt.%, N=12). Composition of metals (in wt.%): kamacite (N=11) – Fe 93.69±1.88, Ni – 5.76±1.86, Co – 0.56±0.07; taenite (N=14) – Fe 72.97±4.06, Ni 26.68±4.11, Co 0.32±0.05; tetrataenite (N=10) – Fe 48.34±1.78; Ni 51.39±1.88, Co 0.20±0.08. Troilite is close to ideal FeS. Pyrrhotite bears up to 2.2 wt.% Ni. Goethite and "hydrogoethite" contain up to 6.6 wt.% NiO and up to 0.7 wt.% CoO.

Classification: (Victor V. Sharygin, SIGM and UrFU). Ordinary chondrite. H5, S2, W2.

Specimens: 24.7 g (2 samples) – UrFU; 10.6 g (1 sample) and thin section – SIGM.