Exchange cations and structural formulae of montmorillonites in the Nakajo acid clay deposit, Niigata Prefecture

Montmorillonites from the Nakajo acid clay deposit were investigated by X-ray diffreaction, chemical analysis and cation exchange methods. Predominant exchange cations in the specimens from the upper horizons of the deposit are Mg and Ca ions, while that in the specimens from the lower horizons is Na ion. Cation exchange reactions of montmorillonites in solutions having the same ion ratios as those of sea water were carried out. Properties of the solution containing exchange cations and ionic population in tetrahedral and octahedral layers are discussed.