MINERALOGICAL CHARACTERIZATION OF PAULINGITE FROM VINARICKA-HORA, CZECH-REPUBLIC

A sample of the zeolite paulingite from the locality Vinaricka Hora wa s investigated by means of chemical, thermal, powder and single crysta l X-ray methods. The fully transparent, colourless to pale yellow crys tals exhibit the form {110} and occur together with phillipsite. The c hemical composition is (Ca2.57K2.28Ba1.39Na0.38)(Al11.55Si30.59O84). 2 7H(2)O. Z = 16 With minor amounts of Mg (<0.05), Sr (<0.13), Mn (<0.01 ), and Fe (<0.04). The chemical differences from previously described paulingites are a high Ba-content, a lower Si/(Al+Fe) ratio of 2.64, a nd a reduced water-content. The calculated density is 2.098 g cm(-3), and the observed refractive index is 1.482(2). The dehydration behavio ur is characterized by a main weight loss from 24-190 degrees C (-11.2 wt.% congruent to 21H(2)O) and a minor weight loss from 190-390 degre es C (-3.1 wt.% 6H(2)O). The rehydration capability was proven up to 1 50 degrees C. The dehydration process during the main weight loss is a ccompanied by a reduction of the cell volume of 11%. The refined latti ce parameters of the X-ray powder data are a = 35.1231(5) Angstrom and a = 33.7485(8) Angstrom of an untreated and a dehydrated sample, resp ectively. A breakdown of the paulingite structure can be observed whil e the remaining water content decomposes. The single crystal X-ray ref inement of this chemically different sample material derived three mai n cation positions, which are inside a so called paulingite or pi-cage (Ca), between 8-rings of neighbouring pi-cages (Ba), and in the centr e of the non-planar 8-rings of the gamma-cage (K). Further partially o ccupied cation positions (Ca,Na) were located in the planar 8-rings of the alpha- and gamma-cages. No positions within the double 8-membered rings were detected. The water is localized around the main cation po sitions and in three clusters of partially occupied sites.