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The Torbernite Minerals as Model Compounds for the Hydrous Layer Silicates

Published online by Cambridge University Press:  01 January 2024

Malcolm Ross
Malcolm Ross*
Affiliation:
U.S. Geological Survey, Washington, D.C., USA
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Abstract

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A number of minerals and compounds of the torbernite group are represented by the formula A(UO2)(As,P)O4·3H2O where A = K+, NH4+ and/or H3O+. Crystal-structure analyses of K(UO2AsO4)·3H2O, NH4(UO2AsO4)·3H2O, and K0·45(H3O)0·55(UO2AsO4)· 3H2O recently completed by Ross and Evans (1964) reveal the exact nature of their atomic arrangements. All three compounds have interlayer structures formed by hydrogen bonding of water molecules into infinite sheets composed of four- and eight-membered rings, isostructural with the [Si8O20]n8n− layers of apophyllite. The interlayer K+, NH4+, and H3O+ ions, instead of entering in between the [UO2AsO4]nn− layers co-ordinated by a hydration sphere of water molecules, are randomly distributed over the water molecule sites. The formula of the interlayer structure is written [(H2O)3A]nn+.

A similar structural scheme may apply to the expanding layer silicates, such as the montmonllonites and vermiculites. For these minerals, particularly those with low to moderate cation-exchange capacity, the potassium and ammonium analogs usually do not fully contract to the 10 Å basal spacing on immersion in K+ or NH4+ solutions, but rather obtain a spacing of 11–14 Å. In these structures it is proposed that a single or double layer of water molecules, arranged in a manner related to one of the silica or ice polymorphs, enters between the 2: 1 layers, the charge being balanced by random distribution of K+, NH4+, and perhaps H3O+ ions over the H2O sites. The formula of the interlayer structure is written [(H2O)b-yAy]nny+ where A = K+, NH4+, and/or H3O+ and ny+ is the charge required to balance that on the 2: 1 layer. Other Group IA or Group IIA cations may also be randomly distributed over water-molecule sites.

Type
Symposium on Structural Aspects of Layer Silicate
Information
Clays and Clay Minerals (National Conference on Clays and Clay Minerals) , Volume 13 , February 1964 , pp. 65 - 71
Copyright
Copyright © The Clay Minerals Society 1964

Footnotes

Publication authorized by the Director, U.S. Geological Survey.

References

Barnes, W. H. (1929) The crystal structure of ice between 0°C and ~183°C, Proe. Roy. Soc. [London) A 125, 670–93.Google Scholar
Beintema, J. (1938) On the composition and the crystallography of autunite and the meta-autunites, Rec. trav. chim. 57, 155–75.Google Scholar
Bernal, J. D., and Fowler, R. H. (1933) A theory of water and ionic solution, with particular reference to hydrogen and hydroxyl ions, J. Chem. Phys. 1, 515–48.Google Scholar
Brady, G. W., and Krause, J. T. (1957) Structure of solutions, I, J. Chem. Phys. 27, 304–8.CrossRefGoogle Scholar
Buslaeva, M. N., and Samoilov, O. Ya. (1961) Coordination numbers of certain ions in aqueous solutions, and effect of temperature on them, J. Structural Chem. 2, 510–15.Google Scholar
Crute, M. V., and Calvert, L. D. (1964) The crystal structure of ice-II, American Crystallographic Association, Program and Abstracts, Ann. Meet., p. 65.Google Scholar
Hendricks, S. V., and Jefferson, M. E. (1938) Structures of kaolin and talc-pyrophyllite hydrates and their bearing on water sorption of the clays, Am. Mineralogist 23, 863–75.Google Scholar
Kamb, W. V., and Datta, S. K. (1960) Crystal structures of the high-pressure forms of ice, Ice III, Nature 187, 140–1.CrossRefGoogle Scholar
Macey, H. H. (1942) Clay-water relationships and the internal mechanism of drying, Trans. Brit. Ceram. Soc. 41, 73–121.Google Scholar
Peterson, S. W., and Levy, H. A. (1957) A single-crystal neutron diffraction study of heavy ice, Acta Cryst. 10, 70–6.CrossRefGoogle Scholar
Ross, M., and Evans, H. T. Jr. (1964) Studies of the torbernite minerals (I). The crystal structure of abernathyite and the structurally related compounds NH4(UO2AsO4) · 3H2O and K(H3O)(UO2AsO4)2·6H2O, Am. Mineralogist. 49, 1578–1602.Google Scholar
Ross, M., and Evans, H. T. Jr. (1965) Studies of the torbernite minerals, (III), Role of the interlayer oxonium, potassium, and ammonium ions, and water molecules, Am. Mineralogist. 50, 1–12.Google Scholar
Wells, A. F. (1954) The geometrical basis of crystal chemistry, Parts 1, 2, 3, 4, Acta Cryst. 7, 536–44, 545-54, 842-8, 849-53.Google Scholar