This chapter gives a bird’s eye view of magnesium. Magnesium is found compounded with other elements. It could be described as a friendly element; that is, it associates with other elements. It exists in seawater as ions of magnesium, most importantly, in magnesium chloride, which is found in seawater, brines, and salt wells. To obtain magnesium from its resources, we have to apply energy in order to retrieve a usable amount of Mg.