ABSTRACT: The tuffs in Miocene sequence around Gördes show zeolite contents up to 80% in 2/3 of the outcroparea. Heulan.dite--elinoptilol.ite contents, in rock samples have been, calculated by the method of quantitative, x-raydiffraction with dolomite internal, standart.., This technique has been `verified, by known additions method. Standardsamples were, prepared with. 4 slides each.., Heulandite-clinoptilolite contents were obtained from the calibration line.which represents 18 standard samples and 72- points., Highest integrated peaks of heulandite-clinqptilolite and dolomite (dspacing of 3.97 Â. and. d spacing of 2.89 Â) have been used in. the calculations,. The error involved in this method, is4.35%. The method was found to be applicable to samples assaying; only more than 5% zeolite.The tuffs in. Gördes, Aynaalan., Hacialidere and Softalar Regions exhibit `the highest heulandite-clinoptilolite contentsbased, on 95 tuff samples calculated by this method, The. zeolite, contents in pumice fragments were found to exhibit40% less zeolite than the whole rock.