Average structure of incommensurately modulated monoclinic lazurite
- Russian Academy of Sciences, Vinogradov Institute of Geochemistry, Siberian Division (Russian Federation)
The average structure of the monoclinic modification of lazurite Ca{sub 1.26}Na{sub 6.63}K{sub 0.04}[Al{sub 6}Si{sub 6}O{sub 24}](SO{sub 4}){sub 1.53}S{sub 0.99}Cl{sub 0.05} (discovered in the Lake Baikal region) incommensurately modulated along the c axis is solved by the single-crystal X-ray diffraction method. The unit-cell parameters are a = 9.069(1) A, b = 12.868(1) A, c = 12.872(1) A, {gamma} = 90.19(1) deg., sp. gr. Pa, R = 6.9%, 2057 reflections. The AlO{sub 4} and SiO{sub 4} tetrahedra form a partially ordered framework. The positions in the cavities of the framework are split and randomly occupied by Na and Ca atoms and the SO{sub 4}, S{sub 2}, S{sub 3}, and SO{sub 2} anionic groups. The structure of the mineral is compared with the superstructure of triclinic lazurite. Conclusions are drawn about the causes of the incommensurate modulation in monoclinic and other lazurites.
- OSTI ID:
- 21091465
- Journal Information:
- Crystallography Reports, Vol. 51, Issue 4; Other Information: DOI: 10.1134/S1063774506040080; Copyright (c) 2006 Nauka/Interperiodica; Article Copyright (c) 2006 Pleiades Publishing, Inc; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7745
- Country of Publication:
- United States
- Language:
- English
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