Environmental petrography is used to characterize the mineralogy, chemistry, texture, structure, and porosity of geological materials using petrographic evaluation techniques including optical microscopy, x-ray powder diffraction (XRPD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), or electron probe microanalysis (EPMA). Environmental petrographic examination can assist environmental investigation and remediation efforts for contaminated environmental media including soil, sediment, bedrock, and groundwater. Several studies in the published literature over the past two decades have documented the occurrence of several minerals that can facilitate the abiotic natural attenuation (ANA) of chlorinated organic compounds in environmental media under certain geochemical conditions. A recent study by others has also documented the ANA of hexavalent chromium via reduction reactions. Petrographic evaluation and geochemical modeling can be used to characterize reactive minerals and local geochemical conditions as part of an evaluation of the potential of a site’s geology to facilitate the in-situ degradation of these contaminates. Reactive minerals identified in the literature to date include a small number of iron sulfide, iron oxyhydroxide, phyllosilicate, or iron carbonate minerals. Samples of selected bedrock formations from across Upstate New York were collected and petrographically evaluated using polarized light microscopy, XRPD, SEM, and EDS. Elemental mapping was performed on several samples via EPMA with EDS and wavelength dispersive spectroscopy (WDS) to further evaluate and illustrate elemental and associated mineral distributions. The findings of our study document the occurrence of previously identified reactive minerals in several bedrock formations in Upstate New York and importantly also document the occurrence of additional minerals that are also likely to function as reactive minerals. A case study in Upstate New York involving an extensive plume of chlorinated organic compounds in bedrock groundwater is used to illustrate an application of petrographic evaluation and geochemical modeling to chemical hydrogeology, including the development and refinement of a hydrogeologic conceptual site model which illustrates upgradient, source area, and downgradient geochemical conditions and observed vertical and lateral trends.