PATOS DE MINAS (Hexaedrito)

Iron

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ACHONDRITE

HEXAEDRITE

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IIAB

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BRAZIL - MG

1925

Iron Meteorite - IIAB Hexahedrite.

PETROGRAFIA:

Patos de Minas is a normal hexahedrite with Neumann lines extending throughout the section. In most places, the lines reach the corroded surface; but in short 1-2 cm lengths, irregular 0.5-1 mm wide remnants of a zone affected by alpha-2 heat can still be recognized. This observation is unequivocal proof that the meteorite has lost about 1-2 mm from its exterior due to weathering. It is out of the question, under the given climatic conditions, that this loss may have occurred between its "fall" in 1925 and 1958 when the mass was reported in the scientific literature. Therefore, Patos was already a significant terrestrial age when it was discovered in 1925. The etched section shows the usual irregular patches of alternating clear and frosty kamacite. In the clear areas, the rhabdites are quite large (prisms with a cross section of 5 to 30 µm), and the Neumann lines are wide, 5-10 µm. Schreibersite itself was not observed. The phosphorus content is estimated to be around 0.2%. Troilite is quite common as angular nodules of 1 to 10 mm and, in these, bluish bars of daubréelite with 0.5-1 mm in width. Sulphides are little damaged and apparently monocrystalline. Source: Buchwald (1975).

GEOQUÍMICA:

Guimarães (1958) reported an analysis, which, although insufficient, indicates the hexahedral nature of the meteorite (5.29% Ni, 0.07% Co, 0.06% P). Source: Buchwald (1975).

CLASSIFICAÇÃO:

Patos de Minas is a somewhat weathered hexahedrite which is apparently related to such well known hexahedrites as Boguslavka and Edmonton (Canada). It should also be compared to Pirapora, another hexahedrite from Minas Gerais, in order to exclude the possibility that Patos and Pirapora are a paired fall. The chance is very small, however, since Patos displays monocrystalline troilite, while Pirapora has shock-melted troilite. Source: Buchwald (1975).

CLASSIFICADORES:

Not reported by the Meteoritical Bulletin Database. According to documents by M. E. Zucolotto and Buchwald (1975), it was Djalma Guimarães (1958) who carried out the first description.

HISTÓRIA:

A metallic meteorite of 32 kg in a semi-prismatic shape with 30 cm in length and 21 x 12 cm in the thickest part, arrived at the Technological Institute of Belo Horizonte as having been the product of a recent fall on the banks of the Córrego do Areado in Patos de Minas, Minas Gerais. It was then described by Djalma Guimarães (1958) who made a preliminary description having given the name Córrego do Areado indicating the place of the fall. However the meteorite, although still showing some grooves due to the atmospheric passage, regmaglites, does not show signs of the melting crust or even the area affected by the heat, indicating that the meteorite has fallen for a long time and that a good part of its surface has been removed by weathering. In 1975 Buchwald, considering that the location of the find and not fall was not precisely located, established the name of the meteorite as being Patos de Minas. However, before 1880, a mass of about 36 kg having the appearance of a magnifying glass taken from the small forges, that is, more or less with the same description of shape and dimensions, was found at Villa de Areado, located a few leagues away from Villa do Carmo do Paranaíba, in Minas Gerais. This mass was in the hands of Father José de Moraes, but meanwhile it was not recognized as a meteorite by Derby because it does not have the structures of Widmanstätten and because it has a lower nickel content than the meteorites usually contain. However, the Patos de Minas meteorite is classified as a hexahedrite precisely because it is poorer in nickel and does not have the typical structure of octahedrite-type meteorites. Therefore, it is believed that due to the proximity of weight, shape and region of the finding, the meteorite Patos de Minas, after being disqualified by Derby, remained semi-forgotten in the region until again being presented as having been seen to 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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