Page "Rubidium-strontium dating" Paragraph 19

The Rb-Sr dating method has been used extensively in dating rocks.

If the initial amount of Sr is known or can be extrapolated, the age can be determined by measurement of the Rb and Sr concentrations and the < sup > 87 </ sup > Sr /< sup > 86 </ sup > Sr ratio.

The dates indicate the true age of the minerals only if the rocks have not been subsequently altered.