Advances in novel mass-spectrometric methods have opened opportunities to identify “isotopic fingerprints” of most metals, and to make use of the complete information they contain. While the feasibility of these new tools has been demonstrated by now, the derivation of robust geologic and environmental information from their application requires substantial additional efforts. Our emphasis is on calibrating these new tools in settings in which we understand the underlying geomorphic and weathering processes, and in laboratory experiments, including the cycling of these elements through plants.