The autogenous grinding method has been progressively employed in mineral dressing plants during the last 15 years. The term has been used with somewhat different meanings. In this paper the author will use it in the most restricted way, for processes where run-of-mine ore (rock) in one step is reduced to a grind product by the action of the ore itself without any other grinding media present. The pebble grinding process where the major part of the ore enters the mill as finely crushed product which is ground further with selected coarse ore pieces acting as grinding media, is not considered autogenous grinding. Processes where a minor amount extraneous media as steel balls is added to supplement an autogenous mill charge will be called semiautogenous.
Autogenous Grinding Mechanisms
Autogenous grinding is at present carried out in tumbling mills of the same types as used in ball mill grinding. The similarities in equipment and procedure have led to the commonly held assumption that the grinding mechanisms are the same in the two processes, with the coarse part of the ore charge taking over the function of the ball charge. This view is largely correct when considering pebble grinding, but the situation