Calcium nitrate is an inorganic compound with the formula Ca(NO3)2(H2O)x. The anhydrous compound, which is rarely encountered, absorbs moisture from the air to give the tetrahydrate. Both anhydrous and hydrated forms are colorless salts. Calcium nitrate is mainly used as a component in fertilizers, but it has other applications. Nitrocalcite is the name for a mineral which is a hydrated calcium nitrate that forms as an efflorescence where manure contacts concrete or limestone in a dry environment as in stables or caverns. A variety of related salts are known including calcium ammonium nitrate decahydrate and calcium potassium nitrate decahydrate.