Studies are presented that investigated environmentally relevant chemistry on pyrite (FeS2), birnessite (MnO2), and nanocrystalline ferrihydrite. Photoelectron spectroscopy, in situ atomic force microscopy, and in situ infrared spectroscopy studies will be presented that address the oxidation of pyrite, arsenite adsorption on birnessite, and carbonate formation of ferrihydrite. Selected results from these studies will bring forward important issues related to the understanding of complex environmental chemistry occurring on mineral surfaces. In the arsenite/birnessite circumstance, for example, batch reaction measurements determined the extent of the conversion of the arsenite to arsenate and the amount of Mn(II) formed during this reductive dissolution process. Atomic force microscopy (AFM) investigated morphology changes during the reactions associated with birnessite as well as the nature of any precipitate phases by using phase imaging. The microscopy was complemented by X-ray photoelectron spectroscopy (XPS) that was able to determine the relative distribution of Mn(IV), Mn(III) and Mn(II) after reaction with As(III). Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was also used to determine the nature of the arsenic-species on the Mn oxide and oxyhydroxide surfaces.