Bench scale flotation tests were conducted to compare different phosphate depressants for both siliceous and carbonaceous phosphates. For a typical Florida siliceous phosphate ore, it was found that starch is ideal for floating fine (-35 mesh) silica from phosphate, while sodium tripolyphosphate may be the best for coarser (+35 mesh) feeds. Sodium tripolyphosphate also appeared to be the most effective depressant for floating dolomite from phosphate under slightly acidic conditions. Based on the results, an all-cationic flotation process was developed and tested on different feeds. A flowsheet for dolomitic phosphate was also developed, in which a sulfonate was used to float dolomite at slightly acidic pHs with sodium tripolyphosphate as a phosphate depressant, followed by amine flotation of silica. Preliminary mineral dissolution and depressant adsorption tests were conducted to explain the mechanism of phosphate depression.