Kanemite was studied by single-crystal X-ray diffraction. The mineral, ideally NaHSi 2 O 5 .3H 2 O, is orthorhombic (space group Pbcn); unit-cell parameters are a = 4.946(3), b = 20.502(15), c = 7.275(3) Aa, with Z = 4. The structure is solved and refined to an R value of 0.058 for 825 independent reflections. The arrangement of atoms consists of alternating (010) sheets of corrugated [Si 2 O 4 OH] (super n-) n and hydrated Na. The silicate sheets contain six-membered rings of HOSiO 3 -SiO 4 units. Sodium atoms coordinate to six water molecules, forming layers of distorted octahedra. Residual electron densities were located that give reasonable positions for four H atoms. One H is part of a silanol group, and the other three H atoms are associated with water bonded to Na. Bonding between the silicate and Na sheets is through hydrogen bonding from H of the Na layer to O of the silicate sheet.

Crystal structure of kanemite, NaHSi2O5•3H2O, from the Aris phonolite, Namibia

CAMARA ARTIGAS, Fernando;
1999-01-01

Abstract

Kanemite was studied by single-crystal X-ray diffraction. The mineral, ideally NaHSi 2 O 5 .3H 2 O, is orthorhombic (space group Pbcn); unit-cell parameters are a = 4.946(3), b = 20.502(15), c = 7.275(3) Aa, with Z = 4. The structure is solved and refined to an R value of 0.058 for 825 independent reflections. The arrangement of atoms consists of alternating (010) sheets of corrugated [Si 2 O 4 OH] (super n-) n and hydrated Na. The silicate sheets contain six-membered rings of HOSiO 3 -SiO 4 units. Sodium atoms coordinate to six water molecules, forming layers of distorted octahedra. Residual electron densities were located that give reasonable positions for four H atoms. One H is part of a silanol group, and the other three H atoms are associated with water bonded to Na. Bonding between the silicate and Na sheets is through hydrogen bonding from H of the Na layer to O of the silicate sheet.
1999
84
1170
1175
http://ammin.geoscienceworld.org/content/84/7-8/1170.abstract
kanemite; X-ray difraction; EMPA; Namibia; hydrogen bonds; crystal structure
GARVIE L.A.J; DEVOUARD B; GROY T.L; CÁMARA F; BUSECK P.R
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/112584
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