Dear Muhammad,

Using XRD you might find Fe in natural clinoptilolite as a minority impurity in form of Fe2O3 or a related hydroxide. To look for cation sites I recommend these two papers below, the first one describes the method and in the second one the application to the location of a number of cations is shown.

Regards,

A. Rabdel Ruiz-Salvador

http://dx.doi.org/10.1021/jp9105772

Locating Extra-Framework Cations in Low-Silica Zeolites by a Combinatorial Approach of the Direct Space Method and Rietveld Refinement: Application to Ni2+ and Co2+ Enriched Clinoptilolite

https://doi.org/10.1016/j.micromeso.2012.01.018

Location of extra-framework Co2+, Ni2+, Cu2+ and Zn2+ cations in natural and dealuminated clinoptilolite