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A new meteoric iron from Piedade do Bagre, Minas Geraes, Brazil

Published online by Cambridge University Press:  14 March 2018

L. J. Spencer
L. J. Spencer*
Affiliation:
Mineral Department, British Museum of Natural History
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Extract

A mass of iron weighing 130 lb., stated to have been found in 1922 near the village of Piedade do Bagre in Minas Geraes, Brazil, and believed to be meteoric, was submitted by Mr. N. Medawar in January 1929 to the Mineral Department of the British Museum for examination. The following description of the mass fully confirms the supposition of its meteoric origin. Unfortunately, only scanty details are available of the circumstances of the finding of the mass. All the information that Mr. Medawar was able to supply is given in the following short note written by Mr. R. J. Bohrer, with a rough sketch-map of the locality.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 22 , Issue 129 , June 1930 , pp. 271 - 282
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1930

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References

page 272 note 1 Another place called ParaopSba. the chief town of the municipio of the same name, is situated 62 kin. south of Curvello.

page 272 note 2 The same character of surface is shown by the gigantic meteoric iron at Hoba in South-West Africa, on the Hoba West farm, 1:2 miles west of Groot-fontein [Min. Abstr., vol. 4, p. 261]. Here the mass is surrounded by a thick layer of scale, which has, obviously been formed by the weathering of the iron. This ‘iron shale’ is well exposed in the sides of the pit that has been dug partly round the mass. It has a thickness of one foot and shows a lamination parallel to the adjacent surface of the unaltered iron from which it is sharply separated. The scale is dark.brown to black with a dark-brown streak and it is slightly magnetic. It shows green nickel stains and is seamed with calcium carbonate from the surrounding surface limestone (Kalahari Kalk) in which the mass is embedded. The meteorite has the form of a roughly rectangular block with its large upper surfaee level with the surrounding ground. A dozen people can walk about on the level surface of the meteorite. Measurements taken by me in September, 1929, are 295 × 284 cm. (about 10 × 9 feet) on the large flat surface, with a thickness at one end of 111-122 cm. and at the other end of 55-75 cm. From these measurements I calculated the weight of the mass to be about 60 metric tons. This considerably exceeds the largest mass (Ahnighito or ‘The Tent’, 36½ tons) of the Cape York (Greenland) meteoric iron, now in the American Museum of Natural History in New York City, which has hitherto been the record size for a meteorite.

page 274 note 1 These ‘cleavages’ in meteoric iron were first observed by W. H. Wollaston in 1816, and have been called ‘Wollaston planes’ by O. A. Derby, Archivos do Museu Nacional, Rio de Janeiro, 1896, vol. 9, p. 114.

page 275 note 1 Belaiew, N. T., Crystallisation of metals. London, 1923, p. 76 Google Scholar [Min. Abstr., vol. 2, p. 87], gives a table of angles showing the relation between the angles of Widmanstätten figures and the orientation of the section-plane. See.also J. Leonhardt, Neues Jahrb. Min., Abt. A, 1928, vol. 58, p. 179 [Min. Abstr., vol. 4, p. 122].

page 277 note 1 Also called ‘Neumann bands’ and ‘Neumann figures’. The earliest use of the term that I have been able to find is by A. Brezina (‘Neumann’schen Figuren) in Jahrb. Geol. Reichsanst. Wien, 1885, vol. 35, p. 199.

page 278 note 1 J. G. Neumann, Ber. Mitt. Freunden Naturwiss. Wien, 1848, vol. 4, p. 86. The detailed account appeared later in Naturwiss. Abhandl. Wien, 1850, vo]. 3, pt. 2, p. 45.

page 278 note 2 Derby, O. A., Archivos do Museu Nacional, Rio de Janeiro, 1896, vol. 9, p. 153.Google Scholar

page 278 note 3 Prior, G. T., Min. Mag., 1926, vol. 21, p. 189.CrossRefGoogle Scholar

page 278 note 4 Carpenter, H. C. H. and Tamura, S., Trans. Inst. Mining & Metall. London, 1928, vol. 37, p. 381, figs. 87-93.Google Scholar [Min. Abstr., vol. 4, p. 239.]

page 278 note 5 W. Haidinger, Sitzungsber. Math.-naturwiss. Cl. Akad. Wiss. Wien, 1855, vol. 15, p. 354.

page 278 note 6 Linck, G., Zeits. Kryst. Min., 1892, vol. 20, p. 209.Google Scholar

page 278 note 7 Smith, S. W. J., Dee, A. A., and Young, J., Proc. Roy. Soc. London, Ser. A., 1928, vol. 121, pp. 477–514, 6 pls. [Min. Abstr., vol. 4, p. 121.]CrossRefGoogle Scholar

page 280 note 1 Prior, G. T., Min. Mag., 1920, vol. 19, p. 55.CrossRefGoogle Scholar

page 280 note 2 O. A. Derby, Notas sobre meteorites Brasileiros. Revista do Observatorio, Rio de Janeiro, 1888, vol. 3, pp. 3-6, 17-20, 33-37. An abstract of this paper was given in Amer. Journ. Sci., 1888, ser. 3, vol. 36, p. 157.

page 280 note 3 G. T. Prior, 1923; Appendix, 1927.

page 281 note 1 Incorrectly listed as ‘San Sebastiano da Boa Vista’.

page 281 note 2 P. Claussen, Notes géologiques sur la province de Minas Geraes au Brésil. Bull. Acad. Sci. Bruxelles, 1841, vol. 8, pt. 1, pp. 322-343. (Fer météorique, pp. 341-343.)

page 282 note 1 Buchner, O., Die Meteoriten in Sammlungen. Leipzig, 1863, p. 56.Google Scholar

page 282 note 2 O. A. Derby, loc. cit., 1888, pp. 35-36.

page 282 note 3 A. Brezina, Die Meteoritensammlung des k.k. mineralogischen Hofkabinetes in Wien am 1. Mai 1885. Jahrb. Geol. Reichsanst. Wien, 1885, vol. 35, pp. 151-276. (Curvello in the Appendix on p. 221.)

page 282 note 4 Wülfing, E. A., Die Meteoriten in Sammlungen. Tubingen, 1897, p. 399.Google Scholar