According to Jefferson Lab, calcium is obtained by replacing the calcium atoms in lime with aluminum atoms. This heated, low-pressure method is much more effective than the original 19th century technique of extracting calcium through electrolysis of mercuric oxide and lime. Both processes yield highly reactive metallic calcium.
Metallic calcium has limited utility because it has volatile reactions to many other substances. Demand for calcium carbonate is much higher because it does not produce such reactions. Unlike metallic calcium, calcium carbonate is naturally abundant throughout the world and does not require electrolytic purification. According to Dr. Doug Stewart, a contributing author for ChemiCool.com, this compound appears in rocks, seashells, pearls and eggshells.
Calcium carbonate has many industrial and agricultural applications. It is a primary ingredient in blackboard chalk, scouring powder and many brands of toothpaste. In small doses, calcium carbonate is non-toxic and provides heartburn relief by neutralizing excess stomach acid. Calcium is essential to healthy teeth and bones, and individuals who do not naturally consume adequate amounts of calcium often augment their diet with calcium supplements.
Calcium chloride has great utility in farming and landscaping. A mixture of calcium chloride and water creates agricultural lime, a high-pH soil additive that increases the nutrient absorption of nearby plants and enriches the soil with valuable nitrogen, potassium and phosphorus.