Vertical roller mills (VRM) have been used extensively for comminuting both cement raw materials and minerals like limestone, clinker, phosphate, manganese, magnesite, feldspar and titanium. These mills combine crushing, grinding, classification and drying operations in one unit and have advantages over conventional machines and literature reports that 15% energy saving is achievable in cement grinding operations when compared to ball milling circuit. Such an improved performance in cement grinding operations encouraged the research studies on ore grinding applications. Within the scope of the study ore grinding performance of the vertical roller mill was investigated with mobile pilot plant. In this context, chalcopyrite ore of a plant having rod and ball milling circuit was ground under different operating modes e.g., air swept and overflow, and process conditions, then samples were collected around the system. The collected samples were characterized in terms of size distributions which were then used in comparing the performances of conventional and VRM systems. This study concluded that 18% saving in specific energy consumption was achievable together with the less wear on the internal components. (C) 2014 Elsevier B.V. All rights reserved.