Crystal structure of chabazite K

The crystal structure of the chabazite K with the formula (K1.33Na1.02Ca0.84)[Al4Si8O24] · 12.17H2O from late hydrothermalites in the Khibiny alkaline massif (Kola Peninsula) is established by X-ray diffraction analysis (CAD4 four-circle diffractometer, λMoK α radiation, graphite monochromator, T=193 K, 2θmax = 70°, R 1 = 0.047 for 4745 reflections) on the basis of experimental data (6265 reflections) obtained from a twin (twinning parameter 0.535(1)): a = 13.831(3) Å, c = 15.023(5) Å, sp. gr. R 3m , Z = 3, ρcalcd = 2.016 g/cm3. It is shown that cations occupy five independent positions in large cavities of the tetrahedral Al,Si,O anionic framework in potassium-rich chabazite. A comparative crystallochemical analysis of chabazites of different composition and origin is performed.