Synchrotron radiation FTIR polarized micro-spectroscopy has been used to investigate natural mica crystals in order to characterize the stretching vibrations of the OH groups and their orientation relative to the mica cleavage (001) plane. A procedure to eliminate undesired interference fringes, typically observed when working with thin single-crystals, was set up using an ad hoe sample preparation, and tested. The naturally high brilliance and high polarization properties of synchrotron radiation allows to study very small flakes and hence offers new analytical possibilities in comparison to conventional powder FTIR spectroscopy.