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Interpretation of the optical absorption spectrum ofNi-substituted lizardites

Published online by Cambridge University Press:  09 July 2018

A. Julg
Affiliation:
Laboratoire de Chimie Théorique, Université de Provence. Place V Hugo, 13331 Marseille Cedex 3, France
O. Julg
Affiliation:
Laboratoire de Chimie Théorique, Université de Provence. Place V Hugo, 13331 Marseille Cedex 3, France

Extract

The spectrum of Ni-substituted lizardite, (Mg,Ni)3Si2O5(OH)4, has been discussed by many authors, who have successively given contradictory interpretations concerning the symmetry of the Ni-sites. Lakshman & Reddy (1973) affirmed that in garnierites Ni is in a tetrahedral site. Faye (1974) rejected this conclusion and showed that Ni2+ occupies an octahedral site. However, the Ni … O distance of 2·01 Å which he deduced from the intensity of the crystal field is unacceptable. Recently, using a completely different approach to the interpretation of the spectrum, Cervelle & Maquet (1982) claimed that Ni2+ occupies a six-coordinated site of C3v symmetry, and concluded that the mean Ni … O distance is 2·06 Å.

The aim of this note is to show that it is possible to interpret the spectrum of Ni-lizardite as arising from a predominantly octahedral field with a weak C2v component which provokes a small increase in width of the absorption bands.

Type
Notes
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1984

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