Except for sulphate, there are also many nitrate raw materials, and magnesium nitrate is one of the most widely used one. Properties Magnesium nitrate is an inorganic hygroscopic salt, which is composed of magnesium, nitrogen and oxygen with the chemical formula Mg(NO3)2. It naturally occurs in caverns and mines as nitro magnesite. This is not a common form, although it could be present in places where guano comes in contact with magnesium rich rock. http://www.crownchampion.com/nitrate-raw-material/