Magnesium nitrate is a hygroscopic salt, meaning that it is able to attract and retain water molecules from its immediate environment. It dissolves in water, and is composed of oxygen, nitrogen and magnesium, and decomposes into oxide, nitrogen dioxide and oxygen when heated. It is often found in caves and mines, especially in areas where guano or bird droppings have come into contact with rocks which contain a high amount of magnesium.
One of the major uses of magnesium nitrate is as an ingredient in some types of fertilizer, although much of it that is used in commercial products is an artificially created and synthesized chemical. Fertilizers containing the chemical are often used in the greenhouse industry, and also for growing plants in water rather than soil, an industry known as hydroponics. It is also widely used in the printing and ceramics industries, and as a catalyst for petrochemical manufacturing.