Hostname: page-component-848d4c4894-r5zm4 Total loading time: 0 Render date: 2024-06-16T16:40:55.251Z Has data issue: false hasContentIssue false

The iron-rich blueschist facies minerals: 2. Howieite

Published online by Cambridge University Press:  05 July 2018

Robert Muir Wood*
Department of Mineralogy and Petrology, Cambridge


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.

Research Article
Copyright © The Mineralogical Society of Great Britain and Ireland 1979

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)


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