The report gives results of sampling and studies of 37 operating and other pits in fresh-water marl in northeastern U.S., and 24 deposits of chalk in chalky limestone, four deposits of shell and coquina, two deposits of caliche, and a large carbonate sludge refuse pile, all in the eastern U.S. The studies related to their potential use in limestone processes for SO2 emission control from fossil fuel combustion. Each sample and its calcined product were investigated for petrography, mineralogy, chemistry, pore structure, and surface area. It was indicated that marls and their calcones should have high reactivities with SO2; because of their ease of production and disaggregation, marls should be given important consideration for use in limestone scrubbing of flue gases at power plants near marl deposits. Chalks and some chalky limestones should also have higher reactivities with SO2 gases than would dense limestone. Carbonate shell materials should not be crushed and used in SO2 scrubbing; however, their calcines are probably as reactive as those of other carbonates. Carbonate waste sludge resembles marl in many properties and is potentially very reactive with SO2, especially in wet scrubbing processes.