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Journal ArticleDOI

Structural Irregularities in Hydrous Magnesium Silicates

01 Feb 1954-Clays and Clay Minerals (Springer Science and Business Media LLC)-Vol. 3, Iss: 1, pp 94-102
TL;DR: The crystal structures of chrysotile, antigorite, attapulgite, sepiolite, vermiculite, and montmorillonite are discussed in the light of the degree to which they resemble chlorite as discussed by the authors.
Abstract: The crystal structures of chrysotile, antigorite, attapulgite, sepiolite, vermiculite, and montmorillonite are discussed in the light of the degree to which they resemble chlorite. The proposal is advanced that the perfection of articulation between tetrahedrally and octahedrally coordinated layers is temperature-sensitive, and that the several crystallizations reflect the degree to which difficulty of articulation limits the growth of particular compositions.
Citations
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Journal ArticleDOI
TL;DR: The 2: 2 lattice building phenomenon in expansible 2: 1 layer silicates relates to layer charge density and crystal size and frequently tends to inhibit the formation of free gibbsite in soil chemical weathering so long as there are expansible layer silicate present to become intercalated with aluminum hydroxide, a weathering phenomenon that may be called an antigibbsite effect as discussed by the authors.
Abstract: Interlayering of 2: 1 layer silicates varies as a function of chemical weathering from the simple, homogeneous K or Na interlayers of micas to the heterogeneous systems of mica intercalated with expanded 2: 1 layer silicates. “Frayed edge” type of weathering at dislocation planes of mica is collated with K release and preferential cation-exchange uptake of K relative to Ca by such expansible layer silicate systems; mica islands maintain alignment of the silica sheet cavities, which facilitates recapture of lattice K. Intercalation of the expanded 2: 1 layer silicates with alumina interlayers appears to be a characteristic function of chemical weathering in soils, with the formation of 2: 1–2: 2 intergrades not only of 14 A spacing but also of swelling 18 A types that give small 12, 14, 18 A and higher spacing peaks (along with the 10 A peak) at 550°C. Interlayer precipitates appear to be characteristic of soil clays, contrasting with “pure” minerals of deposits developed in less “open” environments than those of soils. The “2: 2 lattice building” phenomenon in expansible 2: 1 layer silicates relates to layer charge density and crystal size, and frequently tends to inhibit the formation of free gibbsite in soil chemical weathering so long as there are expansible layer silicates present to become intercalated with aluminum hydroxide—a weathering phenomenon that may be called an “antigibbsite effect”. Accumulation of alumina (possibly with some iron, magnesium, and allophane) as interlayers in 2: 1 minerals of soils is seen as a genetic stage in the 2: 2 → 1: 1 weathering sequence through which kaolinite and halloysite develop in soils.

224 citations

Journal ArticleDOI
TL;DR: In this paper, it is suggested that K+ is adsorbed preferentially to Mg2+ by clays when they have been buried to a depth that is greater than that of the K+ equivalence level.
Abstract: Further x-ray and chemical work on suspended sediment samples and cored samples from the James River and its estuary support earlier proposals by the author. A chlorite-like clay is forming from weathered illite through a mixed-layer illite—vermiculite-chlorite stage, and some illite is seemingly regenerated to a better illite by potassium fixation. Chemical analyses of interstitial water, hydrochloric acid-leachate, and fused samples offer explanations regarding the chemical changes occurring in clays as composition of the environment changes. Magnesium is adsorbed by clays to a far greater degree than potassium in the marine and brackish environment. The variance between clays found in Recent and ancient sediments is related to and explained by the concept of the equivalence level. It is suggested that K+ is adsorbed preferentially to Mg2+ by clays when they have been buried to a depth that is greater than that of the Mg2+ — K+ — equivalence level; above this level Mg2+ is preferentially adsorbed by the clays. The trifold nature of clay minerals in terms of their origin and distribution is briefly discussed.

72 citations


Cites background from "Structural Irregularities in Hydrou..."

  • ...The chlorite is probably highly faulted (Bradley, 1955), becoming better crystallized with increasing depth, thus explaining the sharper and higher 4....

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Journal ArticleDOI
TL;DR: In this article, a regular mixed-layer talc-saponite mineral, contaminated with a certain amount of orthochrysotile, was identified by several methods in the weathering products of a serpentinite rock from Ferriere, Nure Valley (Piacenza Province, northern Italy) and belonging to the “ophiolitic formation of the Italian Apennines.
Abstract: A regular mixed-layer talc-saponite mineral, contaminated with a certain amount of orthochrysotile, was identified by several methods in the weathering products of a serpentinite rock from Ferriere, Nure Valley (Piacenza Province, northern Italy) and belonging to the “ophiolitic formation” of the Italian Apennines. The structural formula of the mineral is: [Mg2.80 Fe 0.09 2+ Fe 0.20 3+ ] [Fe 0.07 3+ Al0.45 Si3.48] O10 (OH)2 Mg0.006 Ca0.02 Na0.01 Electron microscopy enables the chrysotile fibres to be distinguished from the platy particles of the talc-saponite mineral. The infra-red method proved very suitable for identifying the talc and saponite constituents of the mixed-layer mineral. The thermal analyses (d.t.a. and d.t.g.) are valuable in revealing the mixed-layer character of the mineral.

19 citations

Journal ArticleDOI
TL;DR: In this paper, the authors describe a mineral that has properties intermediate between those of palygorskite and sepiolite, and its structure seems to be a random intergrowth of both.
Abstract: The smectic clays from Cabo de Gata region, Almeria, Spain, are composed mainly of mont-morillonite, but they contain appreciable quantities of fibrous clay minerals, some of which are of the palygorskite type. However, there also is a mineral that has properties intermediate between those of palygorskite and sepiolite. Its structure seems to be a random intergrowth of both.

18 citations

Journal ArticleDOI
TL;DR: In this paper, the content of kaolinite plus halloysite is differentiated quantitatively from chlorite by differential dissolution, even in those samples wherein each mineral has 500°C heat instability of the 7 A peak.
Abstract: The content of kaolinite plus halloysite is differentiated quantitatively from chlorite by differential dissolution, even in those samples wherein each mineral has 500°C heat instability of the 7 A peak. This differentiation is possible because the structures of kaolinite and halloysite are destroyed on loss of the 7 A peak, producing amorphous material which is rapidly soluble in 0.5 N NaOH, whereas the chlorite structure remains largely intact with only partial dehydration of the octahedral layer. The amorphous residue of kaolinite-halloysite is dissolved from the other mineral components of the heated sample with sodium hydroxide and the dissolved silica and alumina are allocated to kaolinite. The percentages of kaolinite thus obtained for Elliott, B3–C horizon, 2–0.2 μ fraction, are 3.8 and 3.7 based on silica and alumina, respectively. Similarly, the percentages of kaolinite obtained for Buchanan, B1 horizon, 2-0.2 μ fraction, are 14.9 and 13.8 based on silica and alumina, respectively. Collapse of the vermiculite basal spacing to 10 A on K saturation and heating to 300°C, together with the clear differentiation of kaolinite by differential dissolution analysis (D.D.A.) above, removed the possibility of misinterpretation of the chlorite-like diffractometer tracing by kaolinite and vermiculite occurring together. Other clays, from Davidson and Susquehanna soils, had 44 and 42 to 43 percent kaolinite, based on silica and alumina, respectively. The vermiculite and montmoril-lonite contents of soil clay samples are quantitatively determined by specific surface. The mica percentages are based on the K2O after exclusion of potassium in feldspars. Water loss in the 400°C-to-ignition range gives an important quantitative basis for chlorite.

16 citations

References
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Journal Article
W. F. Bradley1
TL;DR: The name attapulgite was applied in 1935 by J. De Lapparentl to a clay mineral which he encountered in fuller's earths from Attapulegus, Georgia and Mormoiron, France as mentioned in this paper.
Abstract: The name attapulgite was applied in 1935 by J. De Lapparentl to a clay mineral which he encountered in fuller's earths from Attapulgus, Georgia, and Mormoiron, France. Objections have been raised, and these objections were recently reviewed by De Lapparent,2 that the material involved does not justify the application of a mineral name. However, no attempt has been made to study the crystal structure. De Lapparent himself has suggested for classification purposes that attapulgite is a layer sil icate related to the micas, but some obvious inconsistencies with the o-ray powder diffraction patterns of the mineral have suggested the desirabil ity of attempting a better explanation. The material used in this investigation was obtained from the Attapulgus Clay Co., Attapulgus, Ga. The raw clay was dispersed and freed of large crystall ine impurit ies by sedimentation. Centrifuge fractions were then obtained, of which particularly the fraction between.1 and.05i/ appeared homo-

453 citations

Journal ArticleDOI
TL;DR: The structure of the chlorites, a group of minerals morphologically similar but distinctly different in chemical composition, is determined using the same methods of investigation as those used in the study of the micas.
Abstract: By the application of the same methods of investigation as those used in the study of the micas,(1) I have determined the structure of the chlorites, a group of minerals morphologically similar but distinctly different in chemical composition. This structure is described in the following paragraphs.

219 citations

Journal ArticleDOI
TL;DR: A structure is formulated for talc, pyrophillite, the micas, and the brittle micas which is substantiated by the x-ray examination of the minerals, explains their remarkable physical properties, and leads to a general chemical formula unifying the widely varying analyses reported for different specimens.
Abstract: With the aid of the general principles(1) governing the structures of complex ionic crystals I have formulated a structure for talc, pyrophillite, the micas, and the brittle micas which is substantiated by the x-ray examination of the minerals, explains their remarkable physical properties, and leads to a general chemical formula unifying the widely varying analyses reported for different specimens. This structure is described in the following paragraphs.

194 citations

Journal ArticleDOI
TL;DR: In this article, the problem of the derivation of the formula of Montmorillonite from existing analyses is discussed and the difficulties can be reduced to different causes, such as:
Abstract: The mineral montmori l lonite belongs to the principal constituents of clays and soils and as such is of very great interest. Many authors have already contributed towards a more accurate knowledge of the chemical composition and of the behaviour of this mineral, but nevertheless several problems of primary importance remain to be solved definitely. There are many difficulties in the derivation of the formula of montmorillonite from the existing analyses. These difficulties can be reduced to different causes:

62 citations