Magnesium is a chemical element, symbol Mg, atomic # 12, atomic weight 24,3050
From the National Institutes of Health
Magnesium is a cofactor in more than 300 enzyme systems that regulate diverse biochemical reactions in the body, including protein synthesis, muscle and nerve function, blood glucose control, and blood pressure regulation [1-3]. Magnesium is required for energy production, oxidative phosphorylation, and glycolysis. It contributes to the structural development of bone and is required for the synthesis of DNA, RNA, and the antioxidant glutathione. Magnesium also plays a role in the active transport of calcium and potassium ions across cell membranes, a process that is important to nerve impulse conduction, muscle contraction, and normal heart rhythm . You can read more here.
The name magnesium originates from the Greek word for a district in Thessaly called Magnesia.
In 1618 during a summer drought, a farmer in England attempted to give his cows water from a well. The cows refused to drink because of the water’s bitter taste, but the farmer noticed that the water seemed to heal scratches and rashes. When the water evaporated, it left a crystalline substance that when ingested had a laxative effect. The name of the region where this occurred is called Epsom Commons and thus the substance became known as Epsom salts and its fame spread. It was eventually recognized as hydrated magnesium sulfate, MgSO4-7H2O.