UNSPECIFIED (1995) SI-AL ORDER IN LEUCITE REVISITED - NEW INFORMATION FROM AN ANALCITE-DERIVED ANALOG. AMERICAN MINERALOGIST, 80 (7-8). pp. 705-714. ISSN 0003-004X

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Abstract

The Si-Al ordering in two contrasting samples of leucite was studied using MAS NMR. One sample was synthesized by performing an ion exchange, in molten KCI, on a natural analcite specimen that had a small distribution of Al next-nearest neighbors (NNN). The other leucite sample was a typical natural specimen from the Alban Hills. In the specimen derived by ion exchange, 45-50% of the Al is on T2 sites with the remainder distributed approximately equally between the TI and T3 sites. The Si-29 peak positions in this sample resolve a debate in the literature over assignment of the more complex Si-29 spectra of natural leucite specimens. It is possible to simulate the Si-29 spectrum of Alban Hills leucite with a wide variety of Al distributions, including either Al ordering onto T2 or Al ordering onto T1 + T3. By analogy with the analcite-derived sample and considering previous neutron and X-ray data, Al ordering onto T2 is considered somewhat more probable than the alternative schemes. Site-ordering information obtained from (27)A1 NMR in an earlier study is not considered reliable because of complications arising from the differing (and uncertain) electric-field gradients at these sites.

Item Type:	Journal Article
Subjects:	Q Science > QE Geology
Journal or Publication Title:	AMERICAN MINERALOGIST
Publisher:	MINERALOGICAL SOC AMER
ISSN:	0003-004X
Date:	July 1995
Volume:	80
Number:	7-8
Number of Pages:	10
Page Range:	pp. 705-714
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/19542

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