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The transformation manganite → pyrolusite

Published online by Cambridge University Press:  05 July 2018

P. E. Champness
P. E. Champness*
Affiliation:
Department of Geology, University of Manchester
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Summary

During the transformation of manganite to pyrolusite the b-axis must contract about 15 %. There is evidence that the shrinkage takes place partly by contraction of the whole crystal, but electron-microscope investigations of natural pyrolusites and of manganite oxidized in the laboratory show that the reaction also involves the formation of lamellar pores about 85 Å apart, parallel to (010) of the original manganite. Thus, although pyrolusite is tetragonal, the a- and b-axes are not microscopically identical, a fact which could explain why, when natural pyrolusite is treated hydrothermally at 200 and 300 °C and 1000 bars, only one orientation of manganite is formed (Dent Glasser and Smith, 1968). The pores and the accompanying distortion of the structure act as a ‘memory’ of the parent phase.

Type
Research Article
Information
Mineralogical Magazine , Volume 38 , Issue 294 , June 1971 , pp. 245 - 248
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2013

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Footnotes

1

This paper was read at the Mineralogical Society meeting ‘Order-Disorder Effects in Minerals’ held in Aberdeen on 18–19 September 1969.

References

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