Comparative dry grinding tests were conducted for two grinding flowsheet options using commercial aggregate as feed material: Option A, using a high pressure grinding roll (HPGR) in closed circuit with air classification, and Option B, using HPGR in closed circuit with a 2.36 mm screen, followed by a locked-cycle Bond test. Bond tests were also carried out on standard crushed feed passing 3.35 mm and 2.36 mm for comparison. The feed for the tests was screened and crushed to pass 10 mm. The air classifier produced a fine product with an 80% passing size (P-80) of around 50 mu m. In order to maintain comparability, the Bond tests were carried out using a 75 mu m closing screen, producing a final product with a P-80 of 57 mu m. In all tests, the power consumption of the HPGR, Bond mill and air classifier were recorded directly using a power meter, while the Bond mill power consumption was also calculated using Bond's third law and other published methods. Testing determined that the specific energy consumption of the Option B circuit was 41.9% greater than Option A when evaluated using power logging, or 26.2% greater when calculated using Bond's law. Option A required 20.8-29.5% less energy per tonne of ore processed than Option B, a conservative estimate due to the finer grind size achieved. Further Bond tests showed that the work indices of standard crushed -3.35 mm and -2.36 mm feed were similar (15.0 and 15.3 kW h/t, respectively), while the HPGR crushed -2.36 mm feed produced a lower work index of 14.0 kW h/t These results agree with observations by other workers that HPGR renders a sample more amenable to comminution, most likely due to the introduction of micro-cracks. Crown Copyright (C) 2014 Published by Elsevier Ltd. All rights reserved.