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American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Putirka, Keith / Swainson, Ian

12 Issues per year

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Volume 83, Issue 5-6


Crystal structure of hexagonal trinepheline—A new synthetic NaAlSiO4 modification

V. Kahlenberg
  • Fachbereich Geowissenschaften (Kristallographie), Universität Bremen, Klagenfurter Strasse, D-28359 Bremen, Germany
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ H. Böhm
  • Institut für Geowissenschaften (Mineralogie), Johannes-Gutenberg-Universität Mainz, D-55099 Mainz, Germany
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
Published Online: 2015-11-13 | DOI: https://doi.org/10.2138/am-1998-5-622


The crystal structure of a synthetic NaAlSiO4 modification has been solved and refined to an R index of 0.020 for 2745 independent reflections. The compound is hexagonal with space group symmetry P61, a = 9.995(2) Å and c = 24.797(4) Å. The crystal showed twinning by merohedry according to m210, which was accounted for in the calculations. The phase was named trinepheline, following prior studies, because the length of its c lattice parameter is three times the length of the c parameter in nepheline, whereas the a parameter is about 10 Å in both phases. The crystal structure is characterized by layers of six-membered tetrahedral rings of exclusively oval conformation. The rings are built up by regularly alternating AlO4 and SiO4 tetrahedra. The stacking of the layers parallel to the c axis results in a three-dimensional network containing channels that are occupied by the Na cations. Although structural similarities with respect to tridymite derivatives can be found, hexagonal trinepheline represents a new type of stuffed tridymite that is not a simple superstructure of nepheline.

About the article

Received: 1997-07-08

Accepted: 1997-12-15

Published Online: 2015-11-13

Published in Print: 1998-05-01

Citation Information: American Mineralogist, Volume 83, Issue 5-6, Pages 631–637, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am-1998-5-622.

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© 2015 by Walter de Gruyter Berlin/Boston.

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