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Some manganese oxide pseudomorphs

Published online by Cambridge University Press:  14 March 2018

R. J. Davis
R. J. Davis*
Affiliation:
Department of Mineralogy, British Museum (Natural History), Cromwell Road, London, S.W. 7
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Summary

Pyrolusite pseudomorphous after manganite occurs at Serro do Navio, Amapa, Brazil. It consists of wedges, flattened on (100) and elongated along [010], twinned on (011) and showing forms d{210}, , b{010}, and f{021} (all indices referred to manganite, in the setting of Dana, 7th edn). The difficulty of distinguishing between pyrolusite pseudomorphous after manganite and after groutite is discussed and also the possible existence of the latter. The distinction was made here by measuring the twinning angle between the pyrolusite lattices using (0kl) precession photographs. Specimens of manganite intergrown with pyrolusite are described and their relative orientations determined. On heating, manganite partly decomposes to a monoclinic phase, a 9·9 Å, b 5·73 Å, c 4·89 Å, β 98°, space group I2, Im, or I2/m.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 36 , Issue 278 , June 1967 , pp. 274 - 279
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1967

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