Tuesday, 10 June 2014

The nature of the Nathdwara Meteorite.

On 25 December 2012 at about 6.20 pm local time a single meteorite fell in a field near the town of Nathdwara in southern Rajastan. The meteorite was an oblong shape, 12 cm along its longest axis, and weighed about 1.5 kg. It was covered by a dark fusion crust, formed by melting of its outer surfaces by friction as it passed through the atmosphere, and when broken apart by local villagers the interior was found to be a grey rocky material.

In a paper published in the journal Geoscience Frontiers on 14 August 2013, Vinod Agarwal of the Department of Geology at Mohanlal Sukhadia UniversityGopalakrishnarao Parthasarathy of the CSIR-National Geophysical Research Institute, M.S. Sisodia of the Department of Geology at Jai Narain Vyas University and Narendra Bhandari of the Physical Research Laboratory in Ahmedabad, describe the results of a study of the composition and mineralogy of the Nathdwara Meteorite.

Original piece after it was collected by the villagers and was slightly broken at top; the diameter of the meteorite piece is about 3 cm, and the length is about 12 cm. Agarwal et al. (2014).

Argawal et al. were able to examine a 30g piece of the Nathdwara Meteorite. This was a chondrite (stoney meteorite) with a largely re-crystalized structure, showing some relict chondrules (spherical mineral grains found in meteorites, thought to have formed from the cooling of molten droplets of minerals in space before the accretion of the material into a meteorite). Mineral grains of olivine, pyroxene and feldspar could be seen in thin section, as could considerable amounts of troilite (an iron sulphide mineral). The meteorite was found to comprise 29.2 % iron by weight, making it an H Chondrite (High iron Chondrite), and its re-crystalized mineralogy leads Argawal et al. to classify it further as an H6 Chondrite (High iron Chondrite with largely re-crystalized chondrules).

(a) Photomicrographs of the thin section of the Nathdwara meteorite under plane polarized light, the scale is given showing the mineral assemblages and the matrix of the meteorite sample (various minerals are indicated as Ole-olivine, Cpxe-clinopyroxene, Troe-troilite, Sple-spinel, and Ilme-ilmenite). (b) Relict skeletal olivine chondrule, and pyroxene. Nicols crossed, porphyritic olivine integrating with the matrix. Agarwal et al. (2014).


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