magnesiumchemical element, atomic number 12, chemical symbol MgThe hardness of water depends principally upon the concentration of calcium and magnesium . There are many minerals needed by the body . Examples are iron , calcium , sodium , potassium , phosphorus , and magnesium. Doctors at Leicester Royal Infirmary are to assess the benefits of giving magnesiumto heart attack victims immediately after an attack . Drought resulted in decreased root growth and slower breakdown of soil litter , an important source of magnesium for forest trees . They agree that yellowing needles are caused by magnesium deficiency . Treatment of water utilizing the principle of ion-exchange , whereby the calcium and magnesium ions in water were interchanged with sodium from a solid medium , started with the use of natural zeolites , complex hydrated silicates . made of or containing magnesium alloy soap salt chemical compound sulphate silicate hydroxide carbonate magnesium light bright, intense light using magnesium The array of lights varied in intensity and after one hour they vanished. There was no concrete shape yet the colour was the same as magnesium lights , they were brilliant .