Evaporii

Evaporii are mineral deposits formed by the evaporation of saline waters in endorheic basins, saline lakes, and coastal sabkhas. As water in these basins evaporates, salts reach supersaturation and precipitate, creating layered evaporite sequences that record past climatic and hydrological conditions.

Formation and composition: In seawater-derived systems, the typical sequence starts with halite (rock salt) and gypsum or anhydrite, followed by potash minerals such as sylvite and carnallite as salinity rises. The exact order depends on chemistry, temperature, and the rate of evaporation. Evaporii can include sodium and magnesium salts, sulfates, carbonates, and occasional borates.

Global occurrence: Evaporii deposits are found wherever arid climates or restricted basins promote evaporation. Classic examples include the Zechstein salt beds of Europe and the Salar de Atacama in Chile; others occur in North Africa, the Middle East, and Australia.

Extraction and use: Economically, evaporii are important sources of salt, gypsum, and potash fertilizers. Mining typically uses solar evaporation ponds to concentrate brines, followed by crystallization and separation of minerals. Some deposits are mined underground after dissolution of brines. Environmental concerns include water use, land disturbance, and brine disposal.

Relation to evaporites: Evaporii are part of the broader evaporite family of sedimentary rocks formed by evaporation-driven precipitation. See also evaporite deposits for related concepts.