Studies the development of a rapid method to map spectral reflectance variations caused by gypsum on carbonate rock building and monument surfaces. Chemical analysis of gypsum concentration on the lower surface of test stones by the Argonne National Laboratory (ANL) will be used to relate spectral reflectance to the amount of gypsum present. Then, these data will be compared to physical (ANL) and chemical (United States Geological Survey) measurements of deterioration of the upper surfaces to relate spectral reflectance to stone damage. An adequately calibrated mapping method would permit quantitative studies of the spatial distribution of gypsum on building surfaces.