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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
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.
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- Copyright © The Mineralogical Society of Great Britain and Ireland 1998
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