Abstract: A device for primary separation of valuable ore material from gravel or other waste in placer mining prior to sluicing. The separator comprises a frame having sides and front and back ends and adapted to be inclined at an angle to the horizontal during operation. A material entrance is provided at the elevated end. A screen comprising a plurality of hinged rigid plates, laterally extending across the frame, extends from side to side and front to back of the frame and is supported within the frame. The end of the screen at the elevated end of the separator is secured to the frame. The plates are spaced from adjacent plates a pre-determined distance. Screen distortion means comprising a plurality of spaced rows of rounded projections are mounted on the carriage. These projections bear against the bottom surface of the screen whereby, during operation, they move with the carriage back and forth beneath the hinged plates to create a wave action on the screen to move material across the screen from front to back.