High pressure DTA experiments show that the dehydroxylation of kaolinite in dry runs with P(Total) = P(argon) proceeds at 525°C and 1 bar to 627°C at 30.5 bars. Further increase in pressure slowly increases the dehydroxylation temperature, at 5270 bars it occurs at 670°C. Under conditions of P(Total) = P(H₂O), dehydroxylation occurs at 650°C at 46.5 bars and 520°C at 1088 bars after which it increases to 571°C at 5716 bars. The results are explained by postulating the presence of a liquid-like, meta-liquid phase, having a pressure-dependent H₂O solubility. P-T relations of the kaolinite dehydroxylation reactions are best explained by assuming that they are metastable equilibrium reactions around a metastable invariant point at 625°C and 25 bars and a singular point at 640°C and 40 bars.