Cleaning index values provide valuable information for assessing the ability to concentrate a mineral in an ore using a given physical property and for selecting the appropriate separation technology. In response to the recent developments of advanced froth flotation technologies and flotation characterization procedures, a flotation index (FI) has been developed which can be utilized to quantitatively assess the flotation cleaning potential of a given coal sample. Along with an overall FI value, two separate FI values have been determined for each coal to separately characterize the negative selectivity effects caused by the presence of mixed-phase particles and the suppressed recovery rates caused by a lower degree of hydrophobicity of the coal particles. Separate FI values have been determined for ash and sulfur cleaning, which indicate the superior ash cleaning and relatively inferior sulfur cleaning performances achievable by froth flotation.