Sodium chloride
In salt (NaCl) saturated brine, leonite can be deposited from magnesium and potassium sulfate mixtures as low as 25 °C. The 25 °C isotherm of the system has leonite surrounded by sylvine, picromerite, astrakanite, epsomite, and kainite. Sodium chloride saturated brines are formed by seawater evaporation, though seawater does not contain enough potassium to deposite leonite this way.