First, we monitored precipitation from a solution containing 0.2 M CaSO 4 and 4.8 M NaCl at 90 °C using in situ scattering (Fig. ). In this scenario, bassanite formed rapidly as the only crystalline phase. Subsequently, the solution was cooled down to T = 35 °C, which eventually induced the precipitation of gypsum. However, at this temperature the gypsum phase had started to form only after an extensive induction time of ~4800 s, and both phases still coexisted for the following 3600 s. This pointed to very slow kinetics of the hydration of bassanite to gypsum, thus explaining its persistence under high-salinity conditions. This stands in opposition to the typical behaviour of this phase in low salt environments, where a short induction time and rapid transformation is typically reported . On the other hand, increasing the temperature to T = 90 °C (> 13000 s), resulted in an almost instantaneous (< 300 s) reconversion of gypsum into bassanite. These cycles were repeated several times, showing a similar duration of the different phase transformations (Fig. ), thus demonstrating the full reversibility of the process.