Artisinal Mine Tunnelling Machines

Placer gold mining methods mineral processing metallurgy.The lower end of the trough is cut off at an angle of about 45 and closed by a screen of sheetiron, b, in which a number of halfinch holes are punched, so that the fine dirt is allowed to pass through while the stones are retained.Below the screen is the upper end of the rifflebox, c, which is usually about 9 feet long, 3 feet wide.