Carbon-14 dating: See Carbon 14 Dating in this web site.Rubidium-Strontium dating: The nuclide rubidium-87 decays, with a half life of 48.8 billion years, to strontium-87.The ratio of calcium formed to argon formed is fixed and known.Therefore the amount of argon formed provides a direct measurement of the amount of potassium-40 present in the specimen when it was originally formed.In old rocks, there will be less potassium present than was required to form the mineral, because some of it has been transmuted to argon.The decrease in the amount of potassium required to form the original mineral has consistently confirmed the age as determined by the amount of argon formed.

With the help of half-life values of a suitable radioisotope of an element, which is present in a rock, or in an artifact, the age of the rock and the artifact can be determined.The formula for the fraction remaining is one-half raised to the power given by the number of years divided by the half-life (in other words raised to a power equal to the number of half-lives).If we knew the fraction of a radioactive element still remaining in a mineral, it would be a simple matter to calculate its age by the formula To determine the fraction still remaining, we must know both the amount now present and also the amount present when the mineral was formed.This is called Therefore the characteristic property of the radioisotope, namely its radioactivity can act as a tag or label, which permits the fate of the element or its compound containing this element to be traced through a series of chemical or physical changes.Some of the application of tracer techniques are discussed below.If three different strontium-containing minerals form at the same time in the same magma, each strontium containing mineral will have the same ratios of the different strontium nuclides, since all strontium nuclides behave the same chemically.