mill stone mining,Mill (grinding) - WikipediaA mill is a device that breaks solid materials into smaller pieces by grinding, crushing, or cutting .. A slightly inclined or horizontal rotating cylinder is partially filled with balls, usually stone or metal, which grind material to the . SAG mills are primarily used at gold, copper and platinum mines with applications also in the lead,.mill stone mining,Arrastra - WikipediaFrom Mining and Scientific Press 52 (1886): 237. Arrastra demonstration in Liberty, Washington, 2007. An Arrastra (or Arastra) is a primitive mill for grinding and pulverizing (typically) gold or silver ore. The simplest form of the arrastra is two or more flat-bottomed drag stones.