7.1. a crushing plant delivered ore to a wet grinding mill for further size reduction. the size of crushed ore (f80) was. 4.0 mm and the s.g. 2.8 t/m 3. the work index of the ore was determined as 12.2 kwh/t. a wet ball mill 1 m 1 m was chosen to grind the ore down to 200 μm. a 30% pulp was made and charged to the mill, which was then.