Brief Description:
Calcium is the fifth most abundant element in the earth's crust, forming more than 3% of it. It is a fairly well-known element as it makes up or is an essential component of many things around--and inside-us, including bones and teeth, and oddly enough, leaves. The metal is a silver color, but it forms a layer of nitride as soon as it is exposed to air. Calcium does not occur free in nature.