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The iron-rich blueschist facies minerals: 2. Howieite

Published online by Cambridge University Press:  05 July 2018

Robert Muir Wood
Robert Muir Wood*
Affiliation:
Department of Mineralogy and Petrology, Cambridge
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Summary

The mineral howieite has a stability range that extends down to pressures at, or even below, those normally considered to represent blueschist facies metamorphism. Its structure, lying somewhere between a chain and a sheet silicate, can accommodate almost complete iron for manganese substitution as well as the more extraordinary ferrous iron for ferric iron substitution, that is tolerated by changes in the hydroxyl and water content of the unit cell. The ideal formula is NaM12 Si12(O,OH)44, where M is principally manganese and iron but may include limited amounts of aluminium and magnesium. Four new localities for howieite have been discovered by the author and the howieites from the eight localities that have been analysed here help complete the compositional spectrum. The most curious crystallographic feature of howieite is that although the structure seems capable of considerable chemical variation, it is only those howieites of approximate NaMn3Fe8(AlMg)1Si12(O,OH)44 composition that are well crystallized, often growing to over 10 mm in length.

Type
Research Article
Information
Mineralogical Magazine , Volume 43 , Issue 327 , September 1979 , pp. 363 - 370
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1979

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References

Agrell, (S. O.), Brown, (M. G.), and McKie, (D.), 1965. Am. Mineral, 50, 278.Google Scholar
Aoki, (Y.) and Isono, (K.), 1968. J. Geol. Soc. Jap. 74, 136.CrossRefGoogle Scholar
Burt, (D. M.), 1973. Geophys. Lab. Yearbook, p. 427.Google Scholar
Klein, (C.,Jr.), 1974. Can. Mineral. 12, 475.Google Scholar
Muir Wood, (R.), 1977. Ph.D. thesis, University of Cambridge.Google Scholar
Roy, (S.), 1968. Econ. Geol. 63, 760.CrossRefGoogle Scholar
Schreyer, (W.) and Abraham, (K.), 1977. Neues Jahrb. Mineral. Abh. 130, 114.Google Scholar
Shannon, (R. D.) and Prewitt, (C. T.), 1969. Acta Crystallogr. B25, 925.CrossRefGoogle Scholar
Wenk, (H. R.), 1973. Naturwiss. 60, 254.CrossRefGoogle Scholar
Wenk, (H. R.) 1974. Am. Mineral. 59, 86.Google Scholar