Abstract
The crystal structure of a sample of talc from Harford County, Maryland, has been determined by least squares refinement from X-ray diffraction photographs. A triclinic cell with a = 5·293, b = 9·179, c = 9·496Å, α = 90·57°, β = 98·91°, γ = 90·03, space group C1̄ is adopted. The layers of the structure have almost monoclinic symmetry but the nearly hexagonal rings of oxygen atoms on the surfaces of the layers, formed by the bases of the silica tetrahedra, are not held in register by interlayer ions as they are in micas but are partly displaced so that the stack of layers forms a triclinic crystal. The hexagons of surface oxygens are distorted by a 3·4° twist of the tetrahedra so that the b axis is 0·2 per cent shorter than in a structure with regular hexagons, and the twist brings the oxygen ions a little closer to the octahedral magnesium ions.
Résumé
La structure cristalline d’un échantillon de talc du Harford County, Maryland, a été déterminée par un raffinement par moindres carrés à partir de clichés photographiques de diffraction des rayons X. On a adopté une maille triclinique de groups C1̄, avec a = 5,293 Å, b = 9,179 Å, c = 9,496 Å, α = 90,57°, β = 98,91° et γ = 90,03°.
Les couches de la structure ont presque une symétrie monoclinique, mais les anneaux d’atomes d’oxygène de surface, d’une forme voisine de l’hexagone, formés par les bases des tétraèdres de silice ne sont pas en correspondance exacte comme ils le sont dans les micas où se trouvent des ions interfeuillets; ils sont au contraire déplacés en partie, si bien que l’empilement des feuillets forme un cristal triclinique. Les hexagones des atomes d’oxygène de surface sont déformés à cause d’une rotation des tétraèdes de 3,4°; ainsi l’axe b est plus court de 0,2% de ce qu’il est dans une structure à hexagones réguliers, et la rotation des tétraèdres rapproche un petit peu les ions oxygène des ions magnésium octaédriques.
Kurzreferat
Die Kristallstruktur einer Talkprobe aus Harford County, Maryland, wurde aus Röntgenbeugungsaufnahmen unter Berechnung der kleinsten Abweichungsquadrate bestimmt. Es wurde eine trikline Zelle mit a = 5,293, b = 9,179, c = 9,496 Å, α = 90,57°, β = 98,91° und γ = 90,03°, Raumgruppe C1 angenommen. Die Schichten dieser Struktur haben fast monokline Symmetrie, doch werden die nahezu hexagonalen Ringe der Sauerstoffatome an den durch die Grundflächen der Si-Tetraeder gebildeten Schichtoberflächen nicht durch Zwischenschichtionen aufeinander ausgerichtet, wie dies bei den Glimmern der Fall ist. Sie sind vielmehr teilweise versetzt, so daß die Schichtfolge einen triklinen Kristall bildet. Die Sechsecke der Oberflächensauerstoffe sind durch eine 3,4°-Drehung der Tetraeder verzerrt, so daß die b-Achse um 0,2% kürzer ist als in einer Struktur mit regelmäßigen Sechsecken. Die Drehung bringt die Sauerstoffionen etwas näher an die oktaedrischen Magnesiumionen heran.
Резюме
Структура кристаллов талька определялась при помощи рентгенографии по образцу из харфордского округа, Мэриланд. Принята триклинная клетка с a = 5,293, b = 9,179, с = 9,496 Å, α = 90,57°, β = 98,91°, γ = 90,03, промежуток группы С 1. Слои структуры имеют почти что моноклинную симметрию, но на поверхности слоев имеются примерно шестигранные кольца атомов кислорода, которые не содержатся в равновесии в межслойных ионах как в слюде, а частично смещены, так что столбик слоя образует триклинный кристалл. Шестигранники поверхностных кислородов искажены скручиванием тетраэдры на 3,4°, таким образом ось b на 0,2 % короче, чем структура с регулярными шестигранниками, а скручивание слегка приближает ионы кислорода к октаэдральным ионам магния.
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References
Aleixandre, V. and Alvarez Estrada, D. (1952) Estudos sobre talcos españoles y sus aplicaciones en dieléctricos para La alta frecuencia. Consejo Superior de Investigaciones Cientificas, Madrid.
Amelinckx, S. and Delavignette, P. (1961) Electron microscope observation of dislocations in talc: J. appl. Phys. 32, 341–351.
Bailey, S. W. (1966) The status of clay mineral structures: Clays and Clay Minerals 14, 1–23.
Brindley, G. W., Oughton, B. M. and Robinson, K. (1950) Polymorphism of the chlorites—I. Ordered structures: Acta Crystallogr. 3, 408–416.
Brindley, G. W. and Wardle, R. (1970) Monclinic and triclinic pyrophyllite: Am. Mineralogist 55, 1259–1272.
Brown, B. E. and Bailey, S. W. (1963) Chlorite polytypism—II. Crystal structure of a one layer Crchlorite: Am. Mineralogist 48, 42–61.
Brown, G. (1965) Significance of recent structure determinations of layer silicates for clay studies: Clay Minerals 6, 73–82.
Burnham, C. W. and Radoslovich, E. W. (1964) Crystal structures of coexisting muscovite and paragonite: Carnegie Institute Year Book, 63, pp. 232–236. Washington D.C. (and privately communicated coordinates).
Coxeter, H. S. M. (1948) Regular Polytopes. Methuen, London.
Deer, W. A., Howie, R. A. and Zussman, J. (1962) Rock Forming Minerals—III. Sheet Silicates. Longmans, London.
Donnay, J. D. H., Donnay, G., Cox, E. G., Kennard, O. and King, M. V. (1963) Crystal Data Determinative Tables. 2nd Edn. Monograph 5. American Crystallographic Association.
Donnay, G., Donnay, J. D. H. and Takeda, H. (1964) Trioctahedral one layer micas—II. Prediction of the structure from composition and cell dimensions: Acta Crystallogr., 17, 1374–1381.
Donnay, G., Morimoto, N., Takeda, H. and Donnay, J. D. H. (1964) Trioctahedral one layer micas—I. Crystal structure of a synthetic ion mica: Acta Crystallogr. 17 1369–1373.
Drits, V. A. (1969) Some general remarks on the structure of trioctahedral micas, pp. 51–59. Proc. (Tokyo) International Clay Conference, Israel U.P., Jerusalem.
El-Attar, H. A., Jackson, M. L. and Volk, V. V. (1972) Fluorine loss from silicates on ignition: Am. Mineralogist 57, 246–252.
Farmer, V. C. (1958) The infra-red spectra of talc, saponite and hectorite: Mineralog. Mag. 31, 829–945.
Farmer, V. C. and Russell, J. D. (1964) The infra-red spectra of layer silicates: Spectrochimica Acta 20, 1149–1173.
Gruner, J. W. (1934) The crystal structures of talc and pyrophyllite: Zeit. Krist. 88, 412–419.
Hamilton, W. C. and Abraham, S. G. (1970) International Union of Crystallography Single Crystal Intensity Project—II. Least squares refinements of structural parameters: Acta. Crystallogr. A26 18–24.
Hendricks, S. B. (1938) On the crystal structure of talc and pyrophyllite: Zeit Krist. 99, 264–274.
Hendricks, S. B. (1940) Variable structures and continuous scattering from layer silicate lattices: Phys. Rev. 57, 448–454
Henry, N. F. and Lonsdale, K. (1952) International tables for X-ray crystallography—1. Symmetry Groups.
Kennard, O., Speakman, J. C. and Donnay, J. D. H. (1967) Primary crystallographic data: Acta. Crystallogr. 22, 445–449.
Kodama, H. and Oinuma, K. (1963) Identification of kaolin minerals in clays by X-ray and infra-red spectroscopy: Clays and Clay Minerals 11, 236–249.
McCauley, J. W. and Newnham, R. E. (1971) Origin and prediction of ditrigonal distortion in micas: Am. Mineralogists, 1626–1638.
Mackenzie, R. C. (1957) Editor The Differential Thermal Investigation of Clays. Mineralogical Society, Clay Minerals Group, London.
Pauling, L. (1930) The structure of micas and related minerals: Proc. Nat.Aca. Sci. U.S. 16, 123–129.
Radoslovich, E. W. (1962) The cell dimensions and symmetry of layer lattice silicates—II. Regression relations: Am. Mineralogist 47, 617–636.
Rayner, J. H. and Brown, G. (1964) Structure of pyrophyllite: Clays and Clay Minerals 13 73–84.
Rayner, J. H. and Brown, G. (1966) Triclinic form of talc: Nature, Lond. 212, 1352–1353.
Rayner, J. H. The crystal structure of phlogopite (to be published).
Ross, M., Smith, W. L. and Ashton, W. H. (1968) Triclinic talc and associated amphiboles from Gouverneur mining district, New York: Am. Mineralogist 53, 751–769.
Sclar, C. B., Carrison, L. C. and Schwartz, C. M. (1965) Phase equilibria in the system MgO-SiO2-H2O, 20–130Kb, 350–1300°C. Basic Sci. Div. American Ceramic Society (Sept. 65).
Shirozu, H. and Bailey, S. W. (1966) Crystal structure of a two layer Mg-vermiculite: Am. Mineralogist 51, 1124–1143.
Smith J. V. and Bailey S. W. (1963) Second review of Al-O and Si-O tetrahedral distances: Acta. Crystallogr. 16, 801–811.
Steinfink, H. (1962) The crystal structure of a trioctahedral mica: phlogopite: Am. Mineralogist 47, 886–896.
Stewart, R. F., Davidson, E. R. and Simpson, W. T. (1965) Coherent scattering for the hydrogen atom in the hydrogen molecule: J. Chem. Phys. 42, 3175–3187.
Takeuchi, Y. and Sadanaga, R. (1966) Structural studies of brittle micas (1) the structure of Xanthophyllite refined: Min. Journ. (Japan) 4, 424–437.
Wardle, R. and Brindley, G. W. (1972) The crystal structures of pyrophyllite, ITc and of its dehydroxylate: Am. Mineralogist 57, 732–750.
Wilkins, R. W. T. (1967) The hydroxyl-stretching region of the biotite mica spectrum. Mineralog. Mag 36, 325–333.
Wilkins, R. W. T. and Ito, J. (1967) Infra-red spectra of some synthetic talcs: Am. Mineralogist 52, 1649–1661.
Zigan, F. and Rothbauer, R. (1967) Neutronenbeugungsmessungen an Brucit: N. Jb. Miner. Mh. 4/5 137–143.
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Rayner, J.H., Brown, G. The Crystal Structure of Talc. Clays Clay Miner. 21, 103–114 (1973). https://doi.org/10.1346/CCMN.1973.0210206
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DOI: https://doi.org/10.1346/CCMN.1973.0210206