The process goes on until a relatively small quantity of water has by instalments dissolved and hydrated the 2CaSO 4 H 2 O, and has deposited CaSO 4.2H 2 O in felted crystals forming a solid mass well cemented together.
Calcium sulphate, CaSO 4, constitutes the minerals anhydrite (q.v.), and, in the hydrated form, selenite, gypsum (q.v.), alabaster (q.v.), and also the adhesive plaster of Paris (see Cement).
These deposits, in addition to common salt, include the following minerals: sylvine, KC1; carnallite, KC1 MgC12.6H20 (transparent, deliquescent crystals, often red with diffused oxide of iron); kainite, K 2 SO 4 MgSO 4 MgC1 2 6H 2 O (hard crystalline masses, permanent in the air); kieserite MgS04 H20 (only very slowly dissolved by water); besides polyhalite, MgSO 4 K 2 SO 4.2CaSO 4.2H20anhydrite, CaSO 4; salt, NaC1, and some minor components.
Deeper down there are successively strata of polyhalite, MgS04 K2S04.2CaS04.2H20, and anhydrite, CaSO 4, interspersed with regular layers of rock-salt; whilst below the anhydrite we have the main rock-salt deposits.