A gas-solid fluidized bed was used for dry dense medium separation of lump iron ore particles based on their floating and sinking in the fluidized bed. The density of the bed was adjusted to different values using mixtures of zircon sand and iron powder as the fluidized media. Float-sink experiments using 30 mm diameter density adjusted spheres in the range of 2100-4500 kg/m(3) in density increments of 100 kg/m(3) were carried out to determine the partition curves, the density of the bed and the probable error (Ep). It was found that the density could be adjusted in the range of 2500-4200 kg/m(3), when the bulk volume fraction of iron powder and the fluidizing air velocity were varied. The Ep values were less than or equal to 0.05, if suitable fluidizing air velocities were chosen. The density of the bed determined using the spheres floating-sinking corresponds to that measured using the height of the fluidized bed. The float-sink performance of lump iron ore particles in the size range of +25-31.5 mm agrees well with the spheres' float-sink performance. The partition curves, separation density and the Ep values were determined for the lump iron ore particles. The Ep value for the ore particle separation was around 0.03. The theoretical Fe-grade recovery (washability) curve for the ore was determined for separation densities between 2500 and 4200 kg/m(3) from the density distribution and Fe content of the lump iron ore particles. The actual Fe-grade and recovery were calculated from the partition curves of the ore particle separation and compared to the theoretical maximum obtainable Fe-grade and recovery. (C) 2010 Published by Elsevier Ltd.