Weathering cause adding the oxygen to the metals and form the oxides of Al, Ca, Mg and Si.

Also the cat ion exchange capacity of the mineral plays a vital role in the chemical weathering. 

Thanks Prof. Towe for your answer.

the weathering of the zeolitic tuffs depends on several factors.. The most important is the diagenetic environment they have been formed.. If you have smectite plus zeolite, then the rock is more friable than the zeolites formed in areas with high hat flow rates, i.e. formatino of K-mordenite that is followed by silica polymorphs such as cristobalite, opal and/or quartz..

Thanks for all for their answers 

Dear Reyad,

The chemical composition of the tuff, the composition of the circulating fluids, the fluids T, pH and eH etc may have a control on the composition of the zeolite mineral formed.

Have a look at e.g. Bish et al,(eds) 2002. Natural zeolites. Mineral. Soc. Am.

As Prof Towe has pointed out Zeolites (hydrous silicates) found in western united states, Tanzania and India (with deccan Traps)  are alterations of volcanic tuff and volcanic glass. Zeolites found in Tanzania are diagentic alteration products of silicic tuffs in Cenozoic lacustrine deposits that formed in highly saline and alkaline waters.

Thank you all for this scientific discussion