Further polymorphism in cronstedtite

Steadman, R.; Nuttall, Philippa

doi:10.1107/s0365110x64000913

Cited by 46 publications

(14 citation statements)

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“…Moreover, if the layers contain ordered or disordered cation vacancies, or are linked by hydrogen bonds, yet a further set of different displacement vectors is introduced. Typical of this latter category are the kaolinite minerals (Bailey, 1963(Bailey, , 1969 cronstedtite (Steadman & Nuttall, 1963, 1964 and chlorite (Bailey & Brown, 1962;Brown & Bailey, 1963;Shirozu & Bailey, 1965).…”

Section: Introductionmentioning

confidence: 99%

Electron-microscope and diffraction studies of polytypism in stilpnomelane

Crawford¹,

Jefferson²,

Thomas³

1977

Acta Cryst Sect A

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Several hitherto unreported, long-period polytypes of the complex layer silicate stilpnomelane have been identified by a combination of electron diffraction and high-resolution lattice-imaging techniques. The rich diversity of polytypes present in a Californian sample comprises two distinct 2-1ayer structures, one possessing triclinic, the other trigonal symmetry, a 3-layer trigonal variant, and further structures of, as yet, undetermined symmetry with 4, 5, 9 and 14 layers in the unit cell. Coherent intergrowths of the 9 and 14-layer polytypes have been observed in bright-field lattice images, and all polytypes show well-ordered electron-diffraction patterns. Specimens from this geological source, as well as two others (North Wales and New Zealand) display, in addition, disordered examples of the accepted, X-ray based, l-layer triclinic structure. The fine details of the stacking arrangements (vector sequences) in the 2 and 3-layer polytypes have been determined from electron-diffraction data, and, from similarities in the variation of contrast with sample thickness in lattice images of 2 and 14-layer structures, it is possible to formulate a model for the structures of the longer-period polytypes.

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Section: Introductionmentioning

confidence: 99%

Electron-microscope and diffraction studies of polytypism in stilpnomelane

Crawford¹,

Jefferson²,

Thomas³

1977

Acta Cryst Sect A

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“…Cronstedtite belongs to 1 : 1 phyllosilicates of the serpentine-kaolinite group (Steadman and Nuttall 1964;Steadman 1964). Its structural formula is: (Fe )O 5 (OH) 4 , where x is usually in the range of 0.5 to 0.8.…”

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confidence: 99%

Polytypism of cronstedtite from Chyňava, Czech Republic

Hybler¹,

Sejkora²

2017

Jour. Geosci.

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Small druses and isolated crystals of cronstedtite in cavities of a quartz-calcite veinlet were encountered in the borehole drilled near Chyňava (central Bohemia, Czech Republic) in 1943-1944. Single crystals were studied by the X-ray diffraction with aid of the four circle diffractometer with an area detector. The interpretation of precession-like images of reciprocal lattice planes produced by the diffractometer software revealed the polytype 2H 1 (of the subfamily -Bailey's group D) as the most abundant. It occurs either as pure or mixed crystals with minor to negligible proportion of the 2H 2 polytype of the same subfamily. Lattice parameters of both polytypes are: a = 5.4907(3), c = 14.1789(9) Å, space groups P6 3 cm (2H 1 ), and P6 3 (2H 2 ). A crystal of the polytype 3T (subfamily A), twinned by reticular merohedry was sparingly found as well. Another unusual mixed crystal of subfamilies C+A contained the 1T polytype (subfamily C), a disordered portion of the subfamily A except for the apical part of the crystal, and small amount of 3T and possible traces of 6T 2 polytypes (subfamily A) in the bottom part. Electron probe microanalysis of selected cronstedtite crystals revealed minor amounts of Cl up to 0.01 apfu (atoms per formula unit), and small amounts of Mg (0.13-0.24 apfu) regardless of the determined polytype.

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“…Probe analyses of cronstedtite (Table II) show wide variations in composition from points several microns apart, reflecting a variety of layer stacking sequences within very small volumes (Steadman and Nuttall, 1964;Bailey, 1975). The main variations are in SiO2 and Fe as FeO, which vary antithetically.…”

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confidence: 99%

A banded iron-formation assemblage containing clinopyroxene, andradite, babingtonite, and cronstedtite

Gole

1982

Mineral. mag.

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Further polymorphism in cronstedtite

Cited by 46 publications

References 0 publications

Electron-microscope and diffraction studies of polytypism in stilpnomelane

Electron-microscope and diffraction studies of polytypism in stilpnomelane

Polytypism of cronstedtite from Chyňava, Czech Republic

A banded iron-formation assemblage containing clinopyroxene, andradite, babingtonite, and cronstedtite

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