In addition to the updated procedures, a new calibration equation is proposed, with calibration factors for pebble crushing, fine feed and autogenous grinding, based on information in the public literature. Detailed descriptions of the test equipment, procedures, and calibration are provided, and it is proposed that this become an open standard procedure for SAG mill hardness testing, particularly for soft to medium-hard ores, over which range the test is most effective. (C) 2013 Elsevier Ltd. All rights reserved.