Magnesium

What it is and where it is found
Due to its high reactivity, magnesium does not occur in elementary form in nature but in the form of carbonate, chloride, sulphate or dolomite.
Magnesium, a firm, silvery and shiny light metal, builds up an oxide layer when it is exposed to air. The melting point is 650°C, the boiling point 1,107°C. With a density of 1.74 g/cm³ it is one third lighter in weight than aluminum and thus is the lightest industrially used metal and the lightest construction material. In contact with oxygen, magnesium powder can spontaneously ignite or explode. Magnesium can be easily deformed and is water-repellent. 

What it is used for
In view of its chemical structure, magnesium is used almost exclusively as an alloying metal.
It hardens aluminum alloys and improves their weldability.
Magnesium powder used in pyrotechnics is an entirely different field of application.

How it is traded
Magnesium is traded in the form of ingots, granules or powders.