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PIEDADE DO BAGRE
BRAZIL - MG
Iron Meteorite - Anomalous Medium Octaedrite, without chemical group.
According to Spencer & Hey (1930), no regmaglite was preserved. The Washington slice confirms the frayed character. No melting crust and no heat-affected alpha-2 zones were preserved. Terrestrial limonite covers the surface as rough deposits 0.1-1 mm thick. The corrosion state is of an extent that one would expect to require thousands of years, even in the Brazilian climate. The etched sections, after chemical attack on the surface, exhibit a medium Widmanstätten Structure with long, straight kamacite lamellae, with a bandwidth of 0.75 ± 0.10 mm. This bandwidth is quite rare and, in itself, would suggest that the meteorite is chemically anomalous. The kamacite has prominent Neumann bands. They are decorated significantly along both sides, probably from taenite and phosphide. The microhardness of kamacite is 173 ± 8. Recrystallization started over many grain limits, but only started to cover a total of less than 0.1% per area. Taenite and plessite cover about 40% per area, mainly in the form of degenerated comb and liquid plessite fields. Microhardness ranges from 250 in taenite to 200 in the duplex fields of "black taenite". Source: Buchwald (1975).
7.50% Ni, 0.39% Co, about 0.07% P, 15 ppm Ga, 26 ppm Ge, 11 ppm lr. Source: Buchwald (1975).
Medium octahedrite with bandwidth 0.75 ± 0.10 mm. Its chemistry was incompatible with the existing chemical groups for siderites, being classified as anomalous without group. For more information, access the source link http://evols.library.manoa.hawaii.edu/bitstream/handle/10524/35870/vol3-Pan-Pie(LO).pdf#page=14. Source: Buchwald (1975).
Not reported by the Meteoritical Bulletin Database. According to Buchwald (1975), the meteorite was first studied by Spencer & Hey (1930).
A mass of 59.1 kg was found in 1922, about 16 km southwest of the village of Piedade do Bagre, in the Curvello city, state of Minas Gerais. Believing it to be a meteorite, Mr. N. Medawar sent a sample in January 1929 to the British Museum's Mineral Department for examination, where it was described by Spencer & Hey (1930) and a sketch map was provided. They presented photographs of the exterior and micrographs of slices recorded and discussed, in particular, the Neumann bands that they believed to have formed with the impact on the ground. They suggested that the mass was associated with the great fireball observed in the Curvello region in 1833. Piedade do Bagre is, however, corroded to the point that it probably has been exposed to a terrestrial environment for thousands of years, thus the event in Curvello in the 19th century and this meteorite may have no relationship. Source: Buchwald (1975)..
Todas as informações que não possuírem fonte especifica, foram extraídas do Meteoritical Bulletin Database.
Todas as imagens possuem direitos autorais.
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