Calcium

Calcium is a silvery alkaline earth metal that reacts readily with air, forming a dark surface coating. In nature, it occurs in compounds: calcium carbonate is a major ingredient of limestone, chalk and seashells, while gypsum is another important calcium mineral. Industry obtains calcium metal by using electricity to break down molten calcium chloride, or by heating calcium oxide with aluminum. The metal helps improve the quality of steel, while calcium compounds are important ingredients in cement. Inside your body, calcium ions help muscles contract and nerves communicate. This essential nutrient comes from foods such as milk, cheese and kale, rather than from the reactive metal.