Kieserite is a natural mineral with the chemical formula MgSO4 • H2O which has its origin in salt deposits found in Germany. These were formed 230 million years ago, when large areas of Germany were covered by sea water.
During the above Zechstein-formation, a period with a hot and dry climate, the water from salt water lagoons, which were cut off from the ocean by shallow bars, evaporated and the salt was crystallised.
With progressing evaporation, carbonates (lime stone and dolomite) and sulphates (gypsum and anhydrite) sedimented first, followed by rock salt (NaCl).
Finally potassium and magnesium containing salts were crystallised and deposited. This process occured recurrently through a number of salt water inflows, forming several salt deposits. These were later on covered by thick layers of clay, which protected the deposits from weathering.
