Facts About Calcium	Word origin: The word calcium is derived from the Latin calx (lime).	Discovery: The Romans prepared lime in the first century but did not recognize it as a metal. That discovery was made in 1808. Jöns Jacob Berzelius and Pontin prepared a calcium amalgam by electrolyzing lime in mercury. When Humphry Davy learned about this he took it a step further and isolated calcium as an impure metal.	Properties of calcium    	Calcium as a metal has a silvery color and is rather hard. It is one of the alkaline earth elements. It readily forms a white coating of nitride in air reacts with water and burns with a yellow-red flame. [See Periodic Table of the Elements]	Calcium has a large number of both natural and manufactured compounds that are widely used.	Calcium is a component of stalactites and stalagmites in caves. Calcium carbonate has high solubility in water that contains carbon dioxide. This solubility causes the deposits of stalactites and stalagmites. It also is responsible for hardness in water.	Sources of calcium	Calcium is the fifth most abundant component of Earth s crust forming about 3 percent of it. It is an essential part of leaves bones teeth and shells. It is never found isolated in nature but is often found combined in minerals such as limestone gypsum and fluorite. Apatite is the fluorophosphate or chlorophosphate of calcium.	As a metal calcium is prepared by electrolysis of fused chloride and calcium fluoride. This lowers the melting point.	Calcium-rich foods	Calcium is an essential nutrient for building strong bones. Calcium-rich bone-building foods include milk yogurt cheese and pudding. Soy beverages and tofu are also fortified with calcium. Dark green vegetables also provide calcium.	Uses of calcium	Pure calcium metal is used as a reducing agent during preparation of other metals such as thorium uranium zirconium and more. It is also used as a deoxidizer a desulfurizer and a decarburizer for various ferrous and nonferrous alloys. Furthermore calcium can be used as an alloying agent for aluminum beryllium copper lead and magnesium alloys. It serves as a  œgetter  for natural gases in vacuum tubes and other suction devices.	Calcium s many natural and manufactured compounds are widely used in a variety of industries. Some important compounds arecarbide chloride cyanamide hypochlorite nitrate and sulfide.	Quicklime (CaO) is a highly effective base for chemical refinery and has countless uses. It is made by heating slaked lime  � morphed from limestone  � with carefully added water.	When calcium is mixed with sand it hardens mortars and plasters by absorbing carbon dioxide from the air. Therefore it is an important element in some cements.	(Source: Los Alamos National Laboratory)