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Oriented overgrowth of acicular maghemite crystals on quartz

Published online by Cambridge University Press:  09 July 2018

M. M. Abreu
Affiliation:
Instituto Superior de Agronomia, Tapada da Ajuda, 1399 Lisboa
M. O. Figueiredo
Affiliation:
Centro de Cristalografia e Mineralogia, IICT, 1000 Lisboa
J. C. Waerenborgh
Affiliation:
Departamento de Quimica ICEN-LNETI, 2685 Sacavém, Portugal
J. M. P. Cabral
Affiliation:
Departamento de Quimica ICEN-LNETI, 2685 Sacavém, Portugal

Abstract

Maghemite with acicular morphology occurs as an oriented growth on fresh quartz surfaces in the magnetic sandy fraction of the B horizon of a Typic Rhodoxeralf from southern Portugal. The maghemite was characterized by Mössbauer spectroscopy, X-ray diffraction and electron microscopy (scanning and transmission), and on the basis of a structural similarity between quartz and maghemite, a mechanism has been proposed for the formation of the oriented overgrowth. Correlation with an interpretative chemical model is discussed, assuming active sites over quartz surfaces. Infrared absorption data agree with the proposed models.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1988

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