Radiocarbon decays slowly in a living organism, and the amount lost is continually replenished as long as the organism takes in air or food. Because carbon-14 decays at this constant rate, an estimate of the date at which an organism died can be made by measuring the amount of its residual radiocarbon.

Does carbon dating only work on organic material?

Carbon-14 is a weakly radioactive isotope of Carbon; also known as radiocarbon, it is an isotopic chronometer. C-14 dating is only applicable to organic and some inorganic materials (not applicable to metals).