This paper describes an experimental and modelling investigation of a hydrocyclone for the separation of light and heavy particles in an aqueous slurry. The effects of overflow pressure, feed flow rate, particle size, vortex finder length, and particle concentration are investigated. A model based on the governing conservation equations for mass and momentum is solved using a commercial software package, Ansys 12 Fluid Dynamics. Turbulence is modelled using the large eddy simulation, and the discrete particle model is used to predict the particle separation. It is shown by experimentation and modelling that increasing the vortex finder length results in an increase in the recovery of light particles in the overflow. The recovery of light particles increases as their size increases. Increasing the feed flow rate and decreasing the solid concentration in the feed also improves light particle recovery. A computational model based on LES gave close agreement with experimental results for low overall particle concentration.