***Crystal*** ***structure*** refinement of sanidines

Abstract

The ***crystal*** ***structure*** refinement was done on two different sanidines: a high-K one (K0.826Ba0.048Sr0.040AlSi3O8) from the Khibiny Massif and a high-Na one (K0.42Na0.58Ca0.03AlSi3O8) from Mongolia. Corresponding values of the R-factor in anisotropic approxn. are 3.3 and 4.7%, resp. Verified values of the unit-cell parameters and structural and chem. homogeneity have been studied with electron microscopy, microprobe anal. and the Laue method. The Si/Al ordering indexes for T sites in the structure are: t1o = 0.32 t2o = 0.18 (Khibiny sample) and t1o = 0.27 t2o = 0.23 (Mongolian sample). T1-O and T2-O distances are 1.653(1) and 1.637(1) .ANG., 1.646(1) and 1.637(1) .ANG., resp.; the (K,Na)-O distances are 2.933 and 2.853 .ANG., resp. After comparison of obtained data with results published by P. Fenn and G. Brown (1977) for a synthesized sanidine with a compn. similiar to the Mongolian sample, the authors prefer the structural model with nonsplit M-site atoms.