“…In bi-hydrated Mg-vermiculite, Mg 2+ cations are located in the mid-plane of the interlayer with one sheet of H 2 O molecules on each side of this plane (Type II, Figure ). ,− According to this model, Mg is octahedrally coordinated by six H 2 O molecules, whereas additional H 2 O molecules, which are weakly bound to the cation, are located on the same plane as the six cation-bound H 2 O molecules. − A Type II configuration of H 2 O molecules was also proposed for Na-saturated vermiculite, , and for Na-, Ca-, and Li-rich altered phlogopites …”