Grinding has been one of the areas of major development at Outokumpu's
concentrators. During its early years the company used entirely rod and
hall mills, but due to the high costs of metallic grinding it began the
testing of autogenous grinding as early as the 1950s. In the late-1970s, the company's own modification for two stage
autogenous grinding was ready for industrial use. Surprisingly late, in the
80s - 90s, an interest rose to check also the effects of grinding methods on
flotation results. This paper firstly gives a short history of the development work of
Outokumpu type autogenous grinding, called 'Outogenius'. The effects
of some grinding methods on the process results of two nickel ores are
then reviewed. The tests to date show notable effects of grinding methods
on flotation.