| 摘要 |
The invention is constituted by a drum 6, the axis of which is slightly inclined to the horizontal, along at least two diameters and internally covered with rough materials and raising bars. The sand, during washing, passes through the drum from one end to the other and its heavy ores are retained right along the lower generatrix and in the vicinity of it. At intervals of several hours, the drum is rotated, by means of a bar or a tube engaged in sockets 2, through 180 DEG on its axis, and a chute 8 internal to the drum receives the ore particles which a spray boom 7 located above the chute causes to fall therefrom, and discharges them 10 to the outside. The invention applies particularly to the preconcentration of gold and other ores contained in sand. <IMAGE>
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