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Manganese valency and the colour of the Mn2AsO4(OH) polymorphs eveite and sarkinite

Published online by Cambridge University Press:  05 July 2018

Ulf Hålenius  and
Erika Westlund
Ulf Hålenius
Affiliation:
Department of Mineralogy, Swedish Museum of Natural History, P.O. Box 50007, SE-10405 Stockholm, Sweden
Erika Westlund
Affiliation:
Department of Geology and Geochemistry, Stockholm University, SE-10691 Stockholm, Sweden
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Abstract

Polarized optical absorption spectra of single crystals of the two dimorphic Mn2AsO4(OH)-minerals eveite and sarkinite show that minor concentrations of Mn3+ at the octahedral site determine the colour and cause the distinct pleochroism in green and yellow of eveite. In the sarkinite spectra only absorption bands due to spin-forbidden d-d transitions in Mn2+ at six- and five-coordinated sites are observed, which produce a weak flesh-red mineral colour and a very faint pleochroism.

Keywords

eveitesarkiniteoptical spectroscopyLångbanSweden
Type
Research Article
Information
Mineralogical Magazine , Volume 62 , Issue 1 , February 1998 , pp. 113 - 119
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1998

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