Anew method is described for the determination of Rb* concentrations in silicate rocks by FAAS, matrix effect is not observed with Rb. Standard addition method is performed to analyse silicate samples opened by hydrochloric acid and compared with those of the same samples opened by nitric acid. It emphasized that the rubidium does not exhibit any interference from its matrices especially when we use nitric acid for rock sample attack. Chemical analysis of different rocks is carried out and the obtained Rb data are used to identify the incompatible behavior of the rocks and the tectonic setting environment.