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A structure hierarchy for silicate minerals; sheet silicates

Frank C. Hawthorne, Yulia A. Uvarova and Elena Sokolova
A structure hierarchy for silicate minerals; sheet silicates
Mineralogical Magazine and Journal of the Mineralogical Society (February 2019) 83 (1): 3-55

Abstract

The structure hierarchy hypothesis states that structures may be ordered hierarchically according to the polymerisation of coordination polyhedra of higher bond-valence. A hierarchical structural classification is developed for sheet-silicate minerals based on the connectedness of the two-dimensional polymerisations of (TO (sub 4) ) tetrahedra, where T = Si (super 4+) plus As (super 5+) , Al (super 3+) , Fe (super 3+) , B (super 3+) , Be (super 2+) , Zn (super 2+) and Mg (super 2+) . Two-dimensional nets and oikodomeic operations are used to generate the silicate (sensu lato) structural units of single-layer, double-layer and higher-layer sheet-silicate minerals, and the interstitial complexes (cation identity, coordination number and ligancy, and the types and amounts of interstitial (H (sub 2) O) groups) are recorded. Key aspects of the silicate structural unit include: (1) the type of plane net on which the sheet (or parent sheet) is based; (2) the u (up) and d (down) directions of the constituent tetrahedra relative to the plane of the sheet; (3) the planar or folded nature of the sheet; (4) the layer multiplicity of the sheet (single, double or higher); and (5) the details of the oikodomeic operations for multiple-layer sheets. Simple 3-connected plane nets (such as 63, 4.82 and 4.6.12) have the stoichiometry (T (sub 2) O (sub 5) )n (Si:O = 1:2.5) and are the basis of most of the common rock-forming sheet-silicate minerals as well as many less-common species. Oikodomeic operations, e.g. insertion of 2- or 4-connected vertices into 3-connected plane nets, formation of double-layer sheet-structures by (topological) reflection or rotation operations, affect the connectedness of the resulting sheets and lead to both positive and negative deviations from Si:O = 1:2.5 stoichiometry. Following description of the structural units in all sheet-silicate minerals, the minerals are arranged into decreasing Si:O ratio from 3.0 to 2.0, an arrangement that reflects their increasing structural connectivity. Considering the silicate component of minerals, the range of composition of the sheet silicates completely overlaps the compositional ranges of framework silicates and most of the chain-ribbon-tube silicates.


ISSN: 0369-0148
Coden: MNLMBB
Serial Title: Mineralogical Magazine and Journal of the Mineralogical Society
Serial Volume: 83
Serial Issue: 1
Title: A structure hierarchy for silicate minerals; sheet silicates
Affiliation: University of Manitoba, Department of Geological Sciences, Winnipeg, MB, Canada
Pages: 3-55
Published: 201902
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 270
Accession Number: 2019-026979
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Foundations in mineralogy and crystallography; includes appendices
Illustration Description: illus. incl. 12 tables
Secondary Affiliation: CSIRO Mineral Resources, AUS, Australia
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201915
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