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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Bibliographic Details
Published in:Minerals
Main Authors: Natalia V. Zubkova, Rositsa P. Nikolova, Nikita V. Chukanov, Vladislav V. Kostov-Kytin, Igor V. Pekov, Dmitry A. Varlamov, Tatiana S. Larikova, Olga N. Kazheva, Nadezhda A. Chervonnaya, Gennadiy V. Shilov, Dmitry Yu. Pushcharovsky
Format: Article in Journal/Newspaper
Language:English
Published: MDPI AG 2019
Subjects:
elpidite
microporous zirconosilicate
ion exchange
silver
zeolitic properties
crystal structure
Lovozero alkaline complex
Khan Bogdo alkaline complex
IR spectroscopy
thermogravimetry
Mineralogy
QE351-399.2
Kola Peninsula
Lovozero
kola peninsula
Online Access:https://doi.org/10.3390/min9070420
https://doaj.org/article/3f033efee0564bfa8c377ad0721840e8
Description
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 Si 6 O 15 chains (ribbons) and isolated ZrO 6 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) Å 3 ) are occupied by Na + cations and H 2 O 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) Å 3 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) Å 3 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.

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