A broth containing the sulfate reducing bacterium Desulvibrio Desulfuricans was used to treat samples of reagent calcium sulfate, gypsum-rock specimens, fragments from a marble monument with a black weathered crust rich in gypsum, and a marble monument with a similar crust. Calcite was found to have formed on all treated surfaces suggesting that this microbe has the potential to clean crusted marble monuments while also regenerating calcite, the mineral of the marble. Sem photomicrographs, 4 references.