Water-only cyclones (WOCs) are regarded as affordable separation devices, albeit less efficient than other gravity concentrators, which are suitable for fine coal cleaning. The common opinion prevails that the fundamentals of WOC performance have not yet been explicitly recognized. Studies on separation in WOCs, which are treated as gravity separation devices, have analyzed the approach whereby the specific density of separated particles constitutes the separation criterion. This article proposes an attempt to recognize the separation in WOCs, based on the assumption that the particle settling velocity governs the process results, and by learning the distribution of this characteristic within feed particles, we can explain the limitations of fine coal separation in WOCs.