Comminution tests aim at measuring the grindability of ore samples to be used in describing the variability within an orebody and designing the grinding circuit. Within the geometallurgical context this information is very important for creating a proper model for production planning,management and control of the resource’s exploitation before and during the production.Standard grindability tests require at least 2 kg of ore sample, which is quite a lot at early project stages and therefore often problematic. This presentation will deal with the development of a method for studying comminution behaviour of materials with very small sample amounts.The method uses a small laboratory tumbling mill equipped with a gross energy measurement device. The method evaluation comprises the correlation between rock mechanical testing and grindability test methods. Within this approach textural information from drill cores is used as a classification criterium.Experimental results show that a sample of approximately 350 g already provides relevant information about the grindability behaviour of iron ores in the range of 45 to 55 per cent solids, based on mill charge. The gross energy measured is then used to calculate an equivalent grinding energy. This equivalent energy is further used for predicting the variations in throughput for a given deposit and process.