arrastra

listen to the pronunciation of arrastra
Английский Язык - Английский Язык
A device formerly used by gold-miners for grinding auriferous quartz, crudely resembling a mortar and pestle, with the crushing element dragged around by horse or mule
Drag-stone mill for pulverizing ores to isolate silver by the patio process, apparently used in pre-Columbian America. The silver ore was crushed and ground by mule power in the arrastras (shallow circular pits paved with stone). Large blocks of stone attached by beams to a central rotating post were dragged around the arrastra, reducing the ore to a fine mud. Further steps resulted in the isolating of the silver