Evaporites are sediments that result from the evaporation of saline water. Most evaporites are derived from bodies of sea-water, though saline lakes may also be an important source (e.g. the Great Salt Lake, Utah).
Evaporites start to precipitate when their concentration in water reaches such a level that they can no longer exist as solutes. They precipitate out of solution in the reverse order of their solubilities, such that the order of precipitation is:
- Calcite (CaCO3) and dolomite (CaMg(CO3)2)
- Gypsum (CaSO4) and anhydrite (CaSO4.2H2O)
- Halite (i.e. common salt, NaCl)
- Potassium and magnesium salts
