Metal separating process and apparatus

Abstract From the Canadian patent

Heavy metals such as gold, silver platinum copper, etc. in the free state, are separated from their ore by applying water and the ore in finely divided form to at least three rotating, inclined, spiral grooved discs driven from a common shaft. The grooves are closely spaced and with declining pitch from periphery to an annulus at the center of the disc. The free metal tends to sink to the bottom of the grooves and the lighter ore is washed away as the metal moves along the spiral grooves to the annulus. The free metal and any remaining ore is fed from the annulus to the succeeding disc and the process is repeated.