Clinoptilolite-rich tuffs from the states of Chihuahua and Oaxaca in Mexico were modified with NaCl solutions to improve their ion exchange properties using different conditioning processes. First, the elemental and sodium compositions were identified by both induced coupled plasma atomic emission spectroscopy and neutron activation, respectively. The clinoptilolite-rich tuffs were characterized by scanning electron microscopy and X-ray diffraction and the surface areas were also determined in both tuffs. Effective, internal and external cation exchange capacities were determined. It was found that the elemental composition was different in both zeolitic rocks. A sodium treatment using a 0.1 M NaCl solution and reflux thus, improves effective cation exchange capacities of the Mexican clinoptilolite-rich tuffs. The external and internal cation exchange capacities depend on the size of the particle, as well as the source of the zeolitic rocks. The quaternary ammonium salt (HDTMABr or BCDMACl) considered is important in those determinations.