In our experiments, we followed the phase changes occurring in a solution containing 0.2 M CaSO 4 and 4.8 M NaCl (see SI: Materials and Methods). This choice of solution conditions was based on our previous work, in which we found that bassanite precipitated directly at T > 80 °C, while at T < 80 °C only gypsum was observed . Taking into account the updated solubility calculations (Fig. , SI: Materials and Methods) and our previous experimental results (Fig, ), we selected a narrow window of temperatures, around T = 90 °C, to evaluate the stability of calcium sulfate phases, which was done by performing in situ and time-resolved X-ray scattering/diffraction (Fig. , Fig. )