The most abundant natural zeolite, clinoptilolite, was leached with H 3 PO 4 and then studied by X-ray fluorescence and diffraction, adsorption of NH 3 , thermoprogrammed desorption of NH 3 , 5 7 Fe Moessbauer and Fourier transform infrared spectroscopies, and by 3 1 P, 2 7 Al and 2 9 Si magic-angle spinning nuclear magnetic resonance. The material was purified, because 60% of Fe was extracted, and its crystallinity was preserved. The zeolite surface was covered by dilute short-chain polyphosphate species, containing tetrahedral P, octahedral Al and Ca. The Br nsted acidity was modified by dealumination and creation of POH groups.