Grinding and contact with water or salt solution increased the specific surface (ssa) but lowered the first dehydration effect (escaping up to 150°C) and increased the second dehydration effect (150 to 500°C). The dehydroxylation was moved to lower temperatures and was only ΔM(500–1100°C)=3.7±0.3 % as compared to 5.5% in the parent vermiculite (V). Except ΔM(20–150°C), the mass losses measured at the remaining T ranges, were consistent in the ground samples, thus the grinding for 2 min caused the homogenization of the crystal structure of vermiculite [ΔM(150–500°C)=7.6±0.7%].DTA curves after grinding and cation exchange indicate an important exothermal peak at 795–870°C, its temperature depending on exchangeable cation. It indicates the formation of high temperature phases (enstatite, forsterite, spinel). The lowest temperature of the peak (795°C) was observed in V-gr-Li, here lithium silicate was formed. The highest peak temperature (870°C) was found in V-gr-K, where almost only forsterite developed. These exothermal peaks were very weak in unground V with various exchangeable cations.