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Re-examination of kirwanite: a ferri-ferro-hornblende from Co. Down, Northern Ireland

Published online by Cambridge University Press:  05 July 2018

Rab Nawaz  and
George Ryback
Rab Nawaz
Affiliation:
Department of Geology, Ulster Museum, Belfast BT9 5AB
George Ryback
Affiliation:
42 Bell Road, Sittingbourne, Kent ME10 4EB
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Abstract

X-ray powder, optical, infrared, and chemical data suggest that kirwanite is an amphibole of composition (Na,K)0.10Ca1.80(Fe2+,Mn)3.10Mg0.79Fe1.143+Al0.78Si7.18O22(OH)2 and thus corresponds to ferri-ferro-hornblende (Leake, 1978). The type locality, originally given as the NE coast of Ireland, is most likely Dunmore Head, Co. Down. Kirwanite occurs in the groundmass and the vesicles of variolitic andesite dykes of the Mourne dyke swarm. Thomson's original analysis of kirwanite was probably made on a mixture and the name should not be used for an amphibole species.

Type
Research Article
Information
Mineralogical Magazine , Volume 53 , Issue 370 , April 1989 , pp. 253 - 255
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1989

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