Crystal structure of the NaCa(Fe2+, Al, Mn)5[Si8O19(OH)](OH)7 · 5H2O mineral: A new representative of the palygorskite group
| Autor: | I. A. Verin, Sergey M. Aksenov, Ramiza K. Rastsvetaeva |
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| Rok vydání: | 2012 |
| Předmět: | |
| Zdroj: | Crystallography Reports. 57:43-48 |
| ISSN: | 1562-689X 1063-7745 |
| Popis: | A specimen of a new representative of the palygorskite-sepiolite family from Aris phonolite (Namibia) is studied by single-crystal X-ray diffraction. The parameters of the triclinic (pseudomonoclinic) unit cell are as follows: a = 5.2527(2) A, b = 17.901(1) A, c = 13.727(1) A, α = 90.018(3)°, β = 97.278(4)°, and γ = 89.952(3)°. The structure is solved by the direct methods in space group P $$\bar 1$$ and refined to R = 5.5% for 4168 |F| > 7σ(F) with consideration for twinning by the plane perpendicular to y (the ratio of the twin components is 0.52: 0.48). The crystal chemical formula (Z = 1) is (Na1.6K0.2Ca0.2)[Ca2(Fe 3.6 2+ Al1.6Mn0.8)(OH)9(H2O)2][(Fe 3.9 2+ Ti0.1)(OH)5(H2O)2][Si16O38(OH)2] · 6H2O, where the compositions of two ribbons of octahedra and a layer of Si tetrahedra are enclosed in brackets. A number of specific chemical, symmetrical, and structural features distinguish this mineral from other minerals of this family, in particular, from tuperssuatsiaite and kalifersite, which are iron-containing representatives with close unit cell parameters. |
| Databáze: | OpenAIRE |
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