Various methods are available for separating dolomite from ancient limestones. These include the use of acetic acid buffered with sodium acetate [Peterson, von der Borch and Bien (1966) and Goldsmith and Graf (1958)], the use of phosphoric acid [Degens and Epstein (1964) and Weber (1964)], and the use of dilute HCl [Deffeyes and Martin (1962)]. Unfortunately, these methods are not applicable to separation of dolomite from most Recent carbonate sediments. This is due to (1) the fine grained nature of such sediments, and, (2) the presence of Mg-rich cal-cites. These two factors result in a lack of differential solubility between carbonate phases in the reagents mentioned preventing use of these reagents in dolomite separations.