Autogenous (AG) and Semi-Autogenous (SAG) milling has seen increased use in recent years, especially in large mineral processing operations. These mills typically have a large diameter relative to their length, typically in the ratio or 2 or 2.5 to 1. AG mills employ ore as the grinding media. However, one the challenges with AG mills is that properties, such as hardness and abrasiveness, of the ore can vary, resulting in inconsistent grinding behavior. The addition of steel grinding balls rectifies this situation. This approach is then termed semi-autogenous grinding and the total amount of balls in these mills ranges between 5 and 10 percent of the volume.