Nitrate minerals

(mineralogy) Any of several generally rare minerals characterized by a fundamental ionic structure of NO₃^-; examples are soda niter, niter, and nitrocalcite.

These minerals are few in number and with the exception of soda niter are of rare occurrence. Normal anhydrous and hydrated nitrates occurring as minerals are soda niter, NaNO₃; niter, KNO₃: ammonia niter, NH₄NO₃; nitrobarite, Ba(NO₃)₂; nitrocalcite, Ca(NO₃)₂ · 4H₂O; and nitromagnesite, Mg(NO₃)₂ · 6H₂O. In addition there are three known naturally occurring nitrates containing hydroxyl or halogen, or compound nitrates. They are gerhardtite, Cu₂(NO₃)(OH)₃; buttgenbachite, Cu₁₉(NO₃)₂Cl₄(OH)₃₂&mdot; 3H₂O; and darapskite, Na₃(NO₃)(SO₄) · H₂O. See also Niter; Soda niter.

The natural nitrates are for the most part readily soluble in water. For this reason they occur most abundantly in arid regions, particularly in South America along the Chilean coast. See also Fertilizer.