Clinotobermorite, Ca5[Si3O8(OH)]2 · 4 H2O \p=n-\ Ca5[Si6O17] · 5 H2O, a natural C\p=n-\S\p=n-\H(I) type cement mineral: determination of the substructure
Abstract
The substructure of natural clinotobermorite Ca5[Si3O8(OH)]2 · 4 H2O \p=n-\ Ca5[Si6Ol7] · 5 H2O from the Wessels mine, Kalahari manganese field, South Africa, was determined from single-crystal X-ray data. The diffraction pattern (monoclinic: a = 11.19 Å, b = 7.29 Å, c = 22.46 Å, β = 96.97°) is characterised by rather diffuse reflections of the type hkl with h, k = 2n + 1. The substructure (space group I2/m, Z = 1, a/2 = 5.593(6) Å, b/2 = 3.645(4) Å, c = 22.46(3) Å, β = 96.97(2)°) was solved from the sharp Bragg reflections (hkl, with h, k = 2n) and refined on the basis of 1877 unique reflections to R(F) = 6.7%.
The structure of clinotobermorite is closely related to the one of so called 11 Å tobermorite Ca5Si6O16(OH)2 · 2 H2O (pseudo-orthorhombic, a = 11.17 Å, b = 7.38 Å, c = 22.6 Å). In both minerals layers parallel (001), formed by seven-fold co-ordinated Ca, are flanked on either side by wollastonite-like [Si3O9] single chains (ca. 7.3 Å periodicity along b) creating a sandwich-like assemblage. The short b/2 axis (3.645 Å) and the short a/2 axis (5.593 Å) of the subcell are caused by an overlay of two half-occupied single chains of tetrahedra with one shifted by b/2 against the other. In clinotobermorite the sandwich-like layers are stacked along c yielding an interlayer distance of 4.5 Å with a free aperture of 3.2 Å where additional Ca ions and H2O molecules connect the sandwich units. Clinotobermorite with 4–5 H2O represents a much denser structure than 11 Å tobermorite with only 2 H2O or 14 Å tobermorite with ca. 6 H2O (pseudo-orthorhombic, a = 11.17 Å, b = 7.38 Å, c = 27.94 Å). The substructure of clinotobermorite can be interpreted as either composed of ‘Dreiereinfachketten’ leading to the formula Ca5[Si3O8(OH)]2 · 4 H2O, or of ‘Dreierdoppelketten’ leading to the formula Ca5[Si6O17] · 5 H2O, or of a mixture of both variants.
The surface structure of clinotobermorite was studied by atomic force microscopy (AFM) where low magnifications reveal a complex layering or twinning parallel (001). High resolutions scans parallel (100) establish enhanced contrast fringes with a periodicity of ca. 10 Å interpreted as the repeat distance of the Ca polyhedral layers parallel to c.
© 2015 Oldenbourg Wissenschaftsverlag GmbH, Rosenheimer Str. 145, 81671 München
Articles in the same Issue
- Improved analysis of surface X-ray data
- Combination of α-NbOPO4 type layers with enantiomorphic α′-type layers: the “racemic structure” of α-α′-Nb0.787W0.213OPO4
- Synthese und Kristallstruktur von Mo7Sn12Zn40 – einer kubischen Verbindung mit Ikosaedern aus Ikosaedern
- The structural study of Sr4Fe6O13 using a Weissenberg technique and synchrotron radiation – unusual ionic radii of five-coordinated Fe3+ ions
- Crystal structures of α and β modifications of trichlorophosphazo-N-sulfurylchloride Cl3PNSO2Cl
- Verschiedene Aspekte der Kristallstrukturen von YbV4O8.1 III. Domänenstruktur aus parallel verwachsenen Bereichen der α-und β-Phasen und gruppentheoretische Betrachtung ihrer Symmetrie
- Clinotobermorite, Ca5[Si3O8(OH)]2 · 4 H2O \p=n-\ Ca5[Si6O17] · 5 H2O, a natural C\p=n-\S\p=n-\H(I) type cement mineral: determination of the substructure
- The structure of [C12H14N2]3[BiCl6]2 · 2H2O at room temperature
- Structure of (2S)-1-[(2R)-2,4-diphenyl-4-oxobutylideneamino]-2-(methoxymethyl) pyrrolidine
- Crystal and molecular structure of l-hypaphorine hydroiodide
- The crystal structures of two aluminium chloro-propoxides
- Structural analysis of some benzoxazoles containing strong electron donor-acceptor groups
- Anomalous elastic properties and phase transitions of (NH4)2PF7
- Elements of Inorganic Structural Chemistry. Selected Efforts to predict Structural Features
- Micro/Nanotribology and Its Applications
- Crystal structures. I. Patterns and symmetry
- Liquid Crystals in the Nineties and Beyond
- Books Received
Articles in the same Issue
- Improved analysis of surface X-ray data
- Combination of α-NbOPO4 type layers with enantiomorphic α′-type layers: the “racemic structure” of α-α′-Nb0.787W0.213OPO4
- Synthese und Kristallstruktur von Mo7Sn12Zn40 – einer kubischen Verbindung mit Ikosaedern aus Ikosaedern
- The structural study of Sr4Fe6O13 using a Weissenberg technique and synchrotron radiation – unusual ionic radii of five-coordinated Fe3+ ions
- Crystal structures of α and β modifications of trichlorophosphazo-N-sulfurylchloride Cl3PNSO2Cl
- Verschiedene Aspekte der Kristallstrukturen von YbV4O8.1 III. Domänenstruktur aus parallel verwachsenen Bereichen der α-und β-Phasen und gruppentheoretische Betrachtung ihrer Symmetrie
- Clinotobermorite, Ca5[Si3O8(OH)]2 · 4 H2O \p=n-\ Ca5[Si6O17] · 5 H2O, a natural C\p=n-\S\p=n-\H(I) type cement mineral: determination of the substructure
- The structure of [C12H14N2]3[BiCl6]2 · 2H2O at room temperature
- Structure of (2S)-1-[(2R)-2,4-diphenyl-4-oxobutylideneamino]-2-(methoxymethyl) pyrrolidine
- Crystal and molecular structure of l-hypaphorine hydroiodide
- The crystal structures of two aluminium chloro-propoxides
- Structural analysis of some benzoxazoles containing strong electron donor-acceptor groups
- Anomalous elastic properties and phase transitions of (NH4)2PF7
- Elements of Inorganic Structural Chemistry. Selected Efforts to predict Structural Features
- Micro/Nanotribology and Its Applications
- Crystal structures. I. Patterns and symmetry
- Liquid Crystals in the Nineties and Beyond
- Books Received
