text: MetPetDB  is a relational database and repository for global geochemical data on and images collected from  metamorphic rocks from the Earth's crust. MetPetDB is designed and built by a global community of metamorphic  petrologists in collaboration with  computer scientists at Rensselaer Polytechnic Institute as part of the National Cyberinfrastructure Initiative and supported by the National Science Foundation. MetPetDB is unique in that it incorporates image data collected by a variety of techniques, e.g. photomicrographs, backscattered electron images (SEM), and X-ray maps collected by wavelength dispersive spectroscopy or energy dispersive spectroscopy.