Magnesium is a fairly abundant metallic element. But pure magnesium does not occur in nature. Various minerals contain magnesium compounds. A few of these compounds, primarily magnesium chloride and magnesium sulfate, occur in dissolved form in seawater and in some pools of underground water. Seawater contains 0.13 percent magnesium and provides a practically unlimited source of the metal.
Magnesium plays a vital role in the life processes of plants and animals.
Chlorophyll, which green plants use in photosynthesis, contains magnesium. Plants produce carbohydrates, a class of foods essential to living things, by means of photosynthesis. Magnesium also activates many of the enzymes that speed up chemical reactions in the human body. Magnesium and its alloys are used in manufacturing many products. Their light weight makes them suitable for aircraft and automobile parts and for tools and equipment.