Abstract: A contaminant sorting device for sorting contaminant material such as metal and rocks from process materials such as wood chips which are intended to be subsequently processed, comprises a material receiving surface upon which a layer of material is deposited which material contains both contaminant and process material, an impact sensing device for sensing vibrations of the material receiving surface upon impact of the material thereon, an electronic circuit for distinguishing between signals generated by impact of contaminant material from signals generated by impact of process material and for providing an output signal in response to receipt of a contaminant material signal, a flow diverting plate downstream from the material receiving surface which is activated by the signal produced in response to impact of the contaminant material so that the normal flow path of the layer of material is interrupted so as to divert that portion of material containing contaminant material to a separate receptacle, and ti