The Bond work index (BWI) is a widely recognized method used for selecting comminution equipment, evaluating grinding efficiency, and calculating the required grinding power. Although it is considered an industry standard, Bond did not fully define all steps in his original procedure, which can lead to significant variability in test results. One such undefined aspect is the initial particle size of the test material-specifically, the commonly used 3.35 mm feed size. This raises the question of whether the BWI can be reliably determined using finer samples. In practice, materials with particle sizes smaller than 3.35 mm are often encountered. This study continues previous research by examining whether the proposed model for calculating the BWI on fine samples is applicable to medium-hard ores. The validation of the model on medium-hard samples resulted in an error of less than 1%, confirming its high accuracy.