Evaporite mineral, MgSO4.KCl. 3H2O; sp. gr. 2.1; hardness 2.5–3.0; monoclinic; variable in colour, from white through yellow to reddish; vitreous lustre; crystals rare, usually forms granular masses; occurs widely in salt deposits in association with halite, carnallite, etc. It is used as a fertilizer and as a source of potassium salts.