The Crystal Structure of Sinhalite1

J. H. Fang and R. E. Newnham
Laboratory for Insulation Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, U.S.A.
1Supported by the U.S. Air Force, Aeronautical Systems Division, under Contract AF 33 (616)-8353, and by Advanced Research Projects Agency, Department of Defense, through Contract SD-90.

Summary: The Ceylonese gemstone sinhalite, AlMgBO4, is isomorphous with olivine and chrysoberyl. Aluminium and magnesium are oetahedrally coordinated and boron occupies slightly distorted tetrahedra. Because of size differences, the smaller Al ion can be assigned to the inversion symmetry sites, with Mg in mirror plane positions. Least-squares refinement based on single crystal X-ray data gave an accurate set of atomic coordinates with mean interatomic distances: Al-O 1·90, Mg-O 2·10, B-O 1·49 Å.

Mineralogical Magazine; March 1965 v. 35; no. 269; p. 196-199; DOI: 10.1180/minmag.1965.035.269.22
© 1965, The Mineralogical Society
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