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Structural aspects of the hisingerite-neotocite series

Published online by Cambridge University Press:  09 July 2018

R. A. Eggleton
Affiliation:
Department of Geology, Australian National University, P.O. Box 4, Canberra, ACT 2600
J. H. Pennington
Affiliation:
Department of Geology, Australian National University, P.O. Box 4, Canberra, ACT 2600
R. S. Freeman
Affiliation:
Department of Geology, Australian National University, P.O. Box 4, Canberra, ACT 2600
I. M. Threadgold
Affiliation:
Department of Geology and Geophysies, University of Sydney, Australia

Abstract

Transmission electron microscopy, X-ray radial distribution function analysis, chemical analysis, X-ray absorption edge spectroscopy, and Mössbauer spectroscopy combine to confirm an amorphous or gel structure for minerals of the hisingerite-neotocite series: (Fe,Mn)0.8SiO3.1.2H2O. A framework of (Fe,Mn)O6 octahedra and [SiO4] tetrahedra form hollow spheres, 50–100 Å in diameter, cross-bonded into a physically isotropic solid with as much as 10% interconnected pore space. The outer 10–20 Å of the spheres has a rudimentary structure, possibly marking the onset of segregation into Si-rich and (Fe,Mn)-rich layers. The Broken Hill mineral ‘sturtite’ is an intermediate member of the hisingerite-neotocite series.

Resume

Resume

On a utilisé la microscopie électronique par transmission, l'analyse de la distribution radiale par rayons X, l'analyse chimique, la spectroscopie d'adsorption par rayons X et celle de Mössbauer, en vue d'étudier la structure des minéraux de la série hisingerite-néotocite, amorphes ou sous forme de gel (Fe,Mn)0.8SiO3.1.2H2O. Un réseau d'octaèdres (Fe,Mn)O6 et de tétraèdres [SiO4] forme des sphères creuses de 50 à 100 Å de diamre qui sont relièes entre elles pour former un solide physiquement isotrope; au moins 10% de l'espace poral est ainsi interconnecté. Les parties externes de la sphère (10 à 20 Å) ont une structure rudimentaire avec apparition possible de ségrégation entre feuillets riches en silice et riches en Fe,Mn. Le minéral de Broken Hill appelé ‘sturtite’ est un membre intermédiaire de la série de hisingéritenéotocite.

Kurzreferat

Kurzreferat

Mit Hilfe von Transmissions-Elektronenmikroskopie, Röntgenbeugung, chemischer Analyse, Röntgenspektroskopie und Mößbauer-Spektroskopie wurden für Minerale der Hisingerit-Neotocit-Serie amorphe oder gelartige Strukturen mit der Formel (Fe,Mn)0.8- SiO3.1.2H2O festgestellt. Ein Netz von (Fe,Mn)O6-Oktaedern und SiO4-Tetraedern bildet hohle, kugelförmige Teilchen mit einem Durchmesser zwischen 50 und 100 Å, die in einen physikalisch isotropen Körper mit 10% Zwischenraum-Poren eingebaut sind. Die äußeren 10–20 Å der Kugeln besitzen eine rudimentäire Struktur, die möglicherweise auf die beginnende Trennung zwischen Si-reichen und (Fe,Mn)-reichen Schichten hinweist. Das Broken Hill-Mineral Sturtit ist ein Zwischenglied der Hisingerit-Neotocit-Serie.

Resumen

Resumen

Mediante el uso combinado de microscopia electrónica de transmisión, análisis de rayos X por cálculo de funciones de distribución radial, análisis químico, espectroscopía de bordes de absorción de rayos X y espectroscopía Mössbauer se confirma la estructura amorfa o de gel para minerales de la serie hisingerita-neotocita: (Fe,Mn)0.8SiO3.1.2H2O. Un armazón de octaedros (Fe,Mn)O6 y de tetraedros [SiO4] forman esferas huecas, de 50–100 Å de diámetro, unidas dentro de un sólido fisicamente isótropo con hasta un 10% de espacios huecos inter-conectados. La corteza de las esferas, 10–20 Å, tiene una estructura rudimentaria, lo que probablemente indica el principio de la segregación en láminas ricas en Si y en láminas ricas en (Fe,Mn). El mineral de Broken-Hill ‘sturtita’, es un miembro intermidio de la serie hisingerita-neotocita.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1983

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