BALSAS

Iron

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ACHONDRITE

MEDIUM OCTAHEDRITE

IIIAB

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BRAZIL - MA

1974

Iron Meteorite - Octaedrite Medium IIIAB.

PETROGRAPHY:

Very weathered meteorite, having completely lost its original melting crust and, therefore, the heat affected the alpha-2 zone by weathering. The Widmanstätten structure is well developed, shock-hardened and exhibits an epsilon structure, suggestive of shock intensities above 130 k bar. The microhardness of the HV 366 × 20 is in accordance with this state. Taenite and plessite cover about 25% per area. Some skeletal bodies of schreibersite are present at the grain boundaries. The meteorite is very poor in inclusions at 20 cm2; the only visible inclusion present is a 2 mm troilite nodule, showing multiple twinning due to deformation. Description made by M. E. Zucolotto, Hardy Grunewaldt and Werner G.K. Schultz.

GEOCHEMISTRY:

INAA by Dr. J.T. Wasson (UCLA): Ni (8.43% by weight); Co (0.51% by weight); Ga (20.9 ppm); As (7.24 ppm); Ir (0.397 ppm); Au (0.927 ppm).

CLASSIFICATION:

Balsas is a medium octahedrite (average bandwidth 0.9 mm), setting Balsas as a member of the IIIA group.

CLASSIFIERS:

J. T. Wasson and M.E. Zucolotto

HISTORY:

A mass weighing 41 kg was found by Mario Rodrigues, the foreman on a cattle ranch, during a gathering in mid-1974. The meteorite was at the end of a long furrow in the yard. With great difficulty, he was moved to the farm. The farm is called Fazenda América and is located 53 km W from the Parnaíba River, border of the states of Maranhão and Ceará and 80 km south of Balsas. As the Fazenda belongs to the Balsas district and there is no other city in the vicinity, the proposed name of Balsas was approved by the Meteorological Committee and published in July 1998 in Meteorological Bulletin number 82. In 1982, the mass was acquired by a driver from truck and member of ACAEFE (Carazinhense Association of Astronomy and Studies of Space Phenomena) in the state of Rio Grande do Sul, only in 1997 did Dr. Grunewaldt know the meteorite and reported the discovery to the National Museum of Rio de Janeiro. Description made by M. E. Zucolotto, Hardy Grunewaldt and Werner G.K. Schultz.

All information that does not have a specific source was extracted from the Meteoritical Bulletin Database.

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