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The structural formula of a hydrous amphibole

Published online by Cambridge University Press:  14 March 2018

G. D. Nicholls
Affiliation:
Department of Geology, University of Manchester
J. Zussman
Affiliation:
Department of Geology, University of Manchester

Abstract

The majority of amphiboles conform to the general structural formula X2-3Y5Z8O22(OH,F,Cl)2, where X = Na, K, Ca, Y - Mg, Fe″, Mn, A1, Fe‴, Ti, and Z = Si, A1 or Ti. Two X ions occupy the positions filled by Ca in the ideal tremolite structure; the additional X ions are assumed to occur in the 'A' sites which are vacant in tremolite.

For the amphiboles, therefore, the method most commonly adopted for deriving a formula from a chemical analysis is to assume that a total of 24 anions is present in the formula unit.

Type
Research Article
Copyright
Copyright © 1955, The Mineralogical Society

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