Differential thermal analysis (DTA) of gorceixite from Buffels River, Namaqualand, South Africa, shows a strong endothermic reaction, with minima at 569 and 602°C. Thermogravimetry (TG) show a total weight loss of 14.4%, occurring in two definite steps in the ranges 450–550°C and 550–750°C. Thermo-analytical results indicate that water is present in gorceixite, not in the molecular form but as hydroxyl groups.