短語詞組短語gold placer -mining 采金場placer gold mining 砂金礦開采placer r mining 砂礦淘采beach placer mining industry 海濱砂礦開采業(yè)beach placer mining 海濱砂礦開采method of littoral placer mining 濱海砂礦開采法hydraulic mining of placer 砂礦露天水力開采 返回 placer mining