Crystal Chemistry and Properties of Elpidite and Its Ag-Exchanged Forms

Elpidite from the Lovozero alkaline complex, Kola Peninsula, Russia, and Ag-exchanged forms of elpidite from two different localities (Lovozero and Khan Bogdo, Mongolia) were studied by means of single-crystal X-ray diffraction, electron microprobe analysis, thermogravimetry and IR spectroscopy. All...

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Published in:Minerals (Basel) 2019-07, Vol.9 (7), p.420
Main Authors: Zubkova, Natalia V., Nikolova, Rositsa P., Chukanov, Nikita V., Kostov-Kytin, Vladislav V., Pekov, Igor V., Varlamov, Dmitry A., Larikova, Tatiana S., Kazheva, Olga N., Chervonnaya, Nadezhda A., Shilov, Gennadiy V., Pushcharovsky, Dmitry Yu
Format: Article
Language:English
Subjects:
Cation exchanging
Cations
Chemical bonds
Crystal structure
Dehydration
Humidity
Infrared spectroscopy
Laboratories
Mineralogy
Minerals
Moisture content
Occupancy
Organic chemistry
Potassium
Rubidium
Software
Vibrations
Water chemistry
Water content
X-ray diffraction
Zeolites
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Summary:Elpidite from the Lovozero alkaline complex, Kola Peninsula, Russia, and Ag-exchanged forms of elpidite from two different localities (Lovozero and Khan Bogdo, Mongolia) were studied by means of single-crystal X-ray diffraction, electron microprobe analysis, thermogravimetry and IR spectroscopy. All studied samples retain the heteropolyhedral framework consisting of double Si6O15 chains (ribbons) and isolated ZrO6 octahedra. Zeolitic cavities in the initial elpidite from Lovozero (space group Pbm2, a = 14.6127(7), b = 7.3383(4), c = 7.1148(3) Å, V = 762.94(6) Å3) are occupied by Na+ cations and H2O molecules. Both Ag-exchanged forms are characterized by evident distortions of the heteropolyhedral framework and a strongly disordered arrangement of extra-framework cations which results in the appearance of the 14-14-14 Å unit cell (a = 14.1755(7), b = 14.6306(9), c = 14.2896(7) Å, V = 2963.6(3) Å3 for the Ag-exchanged form of elpidite from Lovozero and a = 14.1411(5), b = 14.5948(4), c = 14.3035(5) Å, V = 2952.04(17) Å3 for the Ag-exchanged form of elpidite from Khan Bogdo) and space group Cmce. Elpidite from both localities demonstrates a high exchange capacity to Ag. Exchanged Ag+ cations preferably occupy the sites that are close to the Na sites in the initial elpidite. The paper also contains a review of crystal chemical data on elpidite and its laboratory-modified forms.
ISSN:2075-163X
2075-163X
DOI:10.3390/min9070420