Kainite (MgSO₄·KCl·3H₂O) is a mineral salt that consists of potassium chloride and magnesium sulfate and is used as a fertilizer. This mineral is dull and soft, is colored white through yellow to red and is found in the Stassfurt salt mines in Saxony, Germany. It is a natural salt occurring in irregular granular masses, and is used as a source of potassium and magnesium compounds.