Magnesium is the world's most readily available metal and occurs naturally in minerals, brines, and seawater. Magnesium metal is prepared commercially by two types of processes. In the first process, magnesium chloride is recovered from the raw materials and converted to metal by molten salt electrolysis. The second process involves the reduction of magnesium oxide with silicon or aluminum at high temperatures. The resulting metal is then cast into a variety of shapes and sizes of ingots, or alloyed with various other metals and made into ingots, slabs, billets, and many extruded shapes. Pure magnesium is used for making aluminum alloys, the desulfurization of steel, the manufacture of ductile iron, and as a reducing agent for the production of other metals. Elemental magnesium is the lightest structural metal. Magnesium alloys are used mainly in die and sand castings, and in the manufacture of wrought products. Alloy composition is varied to obtain the desired physical and mechanical properties for a given application.