Natun Balijan        27.856°N, 95.878°E

Assam, India

Fall: 2017 Jun 05 (04:30 PM IST)

Classification: Ordinary chondrite (L4)

History: Eyewitnesses reported that the Sadiya meteorite fell at about angle of 60º in the S15ºW to N15ºE direction. Detonating sound was heard and the meteorite fell on cultivated land (older flood plains) of the Lohit river. The depth of penetration was about 45 cm and a pit of ~40 cm diameter was formed. The diameter of the pit gradually narrows to about 12 cm with depth. One piece of sample was retrieved from the fall site. Shri Somnath Sharma, Director (Geology), State Unit: Assam, GSI, North Eastern Region (NER), Guwahati- 781005, Assam, India obtained the sample from the office of the Deputy Commissioner (Govt. of Assam), Tinsukia district, Assam, India.

Physical characteristics: The meteorite is nearly spherical (diameter ~15 cm), covered with well-preserved fusion crust (thickness ~1-2 mm), and has near rounded edges. Well-developed surface grooves and regmaglypts are present. Chondrules are also visible to the naked eyes.

Petrography: This meteorite is composed of olivine + orthopyroxene + clinopyroxene + feldspathic glass + Fe-Ni metals (kamacite and taenite) + troilite ± magnetite ± merrillite. The chondrules contain olivine and orthopyroxene, with interstitial spaces (mesostasis) occupied by feldspathic glass + feather-like clinopyroxene. The size of chondrules varies from 400-1000 μm (diameter). The shape of chondrules varies from near circular-elliptical to sub-elliptical and rarely as angular. Chondrule types include Barred Olivine (BO), Porphyritic Pyroxene (PP), Porphyritic Olivine (PO), Porphyritic Olivine Pyroxene (POP) and Granular Olivine (GO), and individual chondrule margins are moderately well defined. Matrix is relatively fine grained and thoroughly recrystallized.

Geochemistry: Olivine, Fo_73-75Fa_25-27; clinoenstatite, En_69-76.7Fs_22-30Wo_1-4; clinopyroxene (augite - diopside), Wo_27-48.8 En_43.7-59 Fs_7.3-13.4); and feldspathic glass (albite to oligoclase), Ab_79.4-86An_10-11Or_4-10 with FeO_T content <= 1 wt%.). Kamacite contains Fe ~84-93% and Ni ~6.5-16% , and taenite contains Fe ~46% and Ni ~ 54%.

Classification: Different textural variants of olivine and orthopyroxene exhibit near consistent mineral chemical compositional range (X_Mg) suggesting Natun Balijan is an equilibrated ordinary chondrite (L4) with localized chemical inhomogeneity.

Specimens: The specimen initially was kept in the safe custody of the office of the Deputy Commissioner (Govt. of Assam), Tinsukia district, Assam, India. Subsequently as per the instruction of the Joint Secretary (to the Govt. of Assam), Science and Technology Department, Dispur, Guwahati-781006, Assam, India vides letter no. STE 164/2001/121 dated 28th July 2017 the sample was handed over to the GSI by the Deputy Commissioner (Govt. of Assam), Tinsukia district, Assam. Shri Somnath Sharma, Director (Geology), State Unit: Assam, GSI, North Eastern Region (NER), Guwahati- 781005, Assam colleted the sample on behalf of the Director General, GSI from the office of the Deputy Commissioner (Govt. of Assam), Tinsukia district, Assam, India. The specimen was officially handed over to the Meteorite & Planetary Science Division (MPSD), 15, A & B Kyd Street, GSI, Kolkata on 14.08.2017 by Shri Somnath Sharma, Director (Geology).