Chemistry of illite/smectite and end-member illite

Chemical data from three different series of diagenetic illite/smectites (I/S), analyzed statistically by two regresion techniques, indicate that the content of fixed-K per illite layer is not constant, but ranges from ∼0.55 per O₁₀(OH)₂ for illite layers in randomly interstratified I/S (R=0; > 50% smectite layers) to ∼1.0 per O₁₀(OH)₂ for illite layers formed in ordered I/S (R>0;