Because of the complex mineralogical composition of natural zeolites and consequently
uneven distribution of different phases and elements in the zeolite tuff, a combination of
microscopic, spectroscopic, and other instrumental techniquesmust be used to fully
characterize the material. The basic information about the accessibility of the pores for
different ions and molecules can be obtained from BET Analysis based on nitrogen
physisorption, which gives information about the BET surface and accessibility of the pores
for different ions and molecules. The BET values usually range from 15 to 40 m2/g [19]. X-ray
powder diffraction analysis allows quantitative determination of mineralogical composition
of zeolitic tuffs, including the type of zeolite,and is crucial for any further application of
natural zeolites. A typical X-ray powder diffractogram is shown on Figure 3. Detailed
studies of some zeolite tuffs from Croatia and Serbia by powder X-ray diffraction and
subsequent quantitative Rietveld refinementphase analyses are shown in Figure 4.