Disorder in natrolites: structure determinations of three disordered natrolites and one lithium-exchanged disordered natrolite
Krogh Andersen, Erik; Krogh Andersen, Inger G.; Ploug-Sørensen, Gudrun
European Journal of Mineralogy Volume 2 Number 6 (1990), p. 799 - 808
published: Dec 19, 1990
manuscript accepted: Sep 17, 1990
manuscript received: Mar 10, 1990
ArtNo. ESP147050206007, Price: 29.00 €
Abstract Single crystal diffraction studies of three natrolite specimens from Uzabanya, Hungary (NaI, NaIII, and NaII) were undertaken. In the study of NaI (a = 18.305(3), b = 18.632(3), c = 6.589(2) Å), 783 diffraction intensities were used (CAD-4 diffractometer, MoKα radiation (λMoKα = 0.71069 Å)) and the structure was refined to R (unweighted) = 0.020, R (weighted) = 0.026. In the study ofNaIII (a = 18.367(2), b = 18.583(1), c = 6.599(3) Å), 1304 diffraction intensities were used and the structure was refined to R (unweighted) = 0.025, R (weighted) = 0.027. In the study of Nail (a = 18.372(2), b = 18.576(2), c = 6.606(3) Å), 847 diffraction intensities were used and the structure was refined to R (unweighted) = 0.018, R (weighted) = 0.026. The three specimens differ in cell constants and in average Si-O and Al-O distances (in NaI Si-O(av)= 1.621 Å, Al-O(av) = 1.739 Å; in NaIII Si-O(av) = 1.636 Å, Al-O(av)= 1.716 Å; in Nail Si-O(av) = 1.638 Å, Al-O(av)= 1.713 Å). The difference in cell constants and in Si-O and Al-O distances are related to the Si/Al order in the materials. Crystals of Nail type were exchanged to the lithium form (LiII) in molten lithium nitrate (the crystals remained preserved). Single crystal studies of the exchanged material (a = 17.704(4), b = 18.540(5), c = 6.495(2) Å) used 775 diffraction intensities. The structure is similar to the structure of the sodium form. The structure was refined to R (unweighted) = 0.029, R (weighted) = 0.041. The lithium coordination is discussed.