PIRAPORA

Iron

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ACHONDRITE

HEXAEDRITE

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IIAB

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BRAZIL - MG

1888

Iron Meteorite - IIAB Hexahedrite.

PETROGRAFIA:

The main mass slightly resembles a triangular prism with the following maximum diameters: 8x7x12 cm. Although the terrestrial weathering has softened the bulges and depressions produced by regmaglites, the meteorite still exhibits a marked difference between its sides. The inner side is concave and covered with regmaglites 10 to 15 mm in diameter, while the outer side is slightly convex and with less depressions. Although these characteristics are not as evident as in Cabin Creek, we can deduce that this meteorite also maintained its preferred orientation during atmospheric flight. This concave part was facing downwards, suffering the impact directly with the air molecules, while the convex parts were left behind. The sections recorded after a chemical attack show that Pirapora is a hexahedrite in which the Neumann Lines extend across the surface, stopping abruptly in the alpha-2 zone affected by the heat. Troilite occurs as nodules and bars. They are altered by shock events for complexes, worn out and aggregates of fine-grained troilite, daubrelite and a little bit of kamacite and schreibersite. Rabdites are common and schreibersites can be found partially broken around the troilite nodules. Source: Buchwald (1975).

GEOQUÍMICA:

Ni 5.45%, Co 0.58%, P 0.30% and traces of S (Ferreira, 1954) and Ni 5.43%, Ga 57.8 ppm, Ge 189 ppm and Ir 30 ppm (Wasson, 1979). Data obtained from the documents of National Museum

CLASSIFICAÇÃO:

Structurally the Pirapora meteorite is classified as a hexahedrite and it was chemically determined to belong to the IIAB group. For more information, access the Handbook of Iron Meteorites link http://evols.library.manoa.hawaii.edu/bitstream/handle/10524/35871/vol3-Pim-Pon(LO).pdf#page=8

CLASSIFICADORES:

Not reported by the Meteoritical Bulletin Database. The meteorite was described by Curvello (1954, 1958) and analyzed by Ferreira, at the Brazilian Academy of Sciences. Description obtained from the documents of M. E. Zucolotto.

HISTÓRIA:

Pirapora was found near from the Pirapora city, state of Minas Gerais, on an unknown date. It was acquired by the Belo Horizonte Institute of Technology in 1950. At the time, it weighed 2.56 kg, already reduced from its original weight and with perforations made by drill, possibly to collect material for analysis. The results of such analyses, if they were carried out, never reached scientific knowledge. In 1953, the petrologist, Dr. Djalma Guimarães, donated the meteorite to the National Museum, RJ. Despite the great interest shown, it was not possible to obtain more detailed information regarding the conditions under which the discovery took place. It was described by Curvello (1954, 1958), with analyses by Ferreira, at the Brazilian Academy of Sciences. In 1975, in his book "Handbook of Iron meteorites", Buchwald based on analysis of elements - traces made by Wasson, shows that there is a great similarity in chemical composition between Pirapora and the siderite Pseudo Angra dos Reis, which weighed about 6.175 Kg and was donated to Pope Leo XIII, 1888, without precise information on its origin, but only with the label Angra dos Reis. The confusion increased when, by carelessness, they added the date of the fall of the famous acondrito of Angra dos Reis. Buchwald believes that both siderites may belong to the same fall. Description obtained from the documents of National Museum.

Todas as informações que não possuírem fonte especifica, foram extraídas do Meteoritical Bulletin Database.

Todas as imagens possuem direitos autorais.

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