Microwave plasma (MWP) and inductively coupled plasma (ICP) have been used as excitation sources in spectroscopic analyses. The results show that MWP and ICP sources are excellent for spectroscopic determinations of a large number of major, minor and trace constituents in various geological materials. The low detection limits, the restricted matrix effects and the large number of elements that can easily be determined in a single process make MWP and ICP spectroscopy superior to atomic absorption and X-ray spectroscopy in many geochemical studies.