The ball load behaviour in a pilot mill is studied under conditions of increasing particle filling, for coarse silica feed (0.8-1.8 mm) and fine silica feed (0.075-0.3 mm), at the mill speeds of 63, 78, 88 and 98% of the critical. An inductive probe is used to obtain the ball load behaviour independent of particles present in the mill. The difference in mill power draw obtained from the coarse and fine particle charges are explained via their load behaviour signals. The effect of particle filling and size on the ball load behaviour is quantified through the toe and shoulder angular positions. Radial segregation of the coarse silica particles to the periphery of the charge occurs. A radial segregation index related to the extent of drop in the inductive probe's signal has been defined and used to quantify radial segregation as a function of particle filling and mill speed. (C) 2008 Elsevier B.V. All rights reserved.