(L. calx, lime) Though lime was prepared by the Romans in the first century under thename calx, the metal was not discovered until 1808. After learning that Berzelius andPontin prepared calcium amalgam by electrolyzing lime in mercury, Davy was able to isolatethe impure metal.

Calcium is a metallic element, fifth in abundance in the earth's crust, of which ifforms more than 3%. It is an essential constituent of leaves, bones, teeth, and shells.Never found in nature uncombined, it occurs abundantly as limestone, gypsum, and fluorite.Apatite is the fluorophosphate or chlorophosphate of calcium.