small charge of steel balls may be added to aid the process — the mill is then called a semiautogenous (SAG) mill. AG/SAG mills are often used as the first stage in a two or multiplestage grinding process, where the second stage is carried out by the ball mill, but they can also be used as a onestage grinder. The absence of, or
The gold in the veins can be in many different forms like nuggets or sheets, or in gold compounds. In recovering gold from vein ore, the ore is first crushed in rod or ball mills. In this process the ore is crushed to a powdery substance from which the gold can be extracted by gravity separation.