an apparatus for dry placer mining to concentrate recoverable metallic constituents , such as gold or silver , from a dry gravel mix containing same is comprised of a frame for supporting and guiding an endless belt along a path including an upwardly inclined segment for receiving gravel particulate ; an endless belt including a woven mesh belt member , a plurality of riffle members disposed in spaced parallel relationship within the intertices of the mesh member , and a composite fabric member disposed in face - to - face contact with the bottom surface of the mesh member ; and a fluidizing member for passing a fluidizing gas upwardly through the endless belt along the inclined segment for fluidizing the gravel particulate and for establishing an electrostatic charge proximate the riffle members . the composite fabric member is specially constructed to permit a proper airflow for fluidizing the particulate and for assisting in the establishment of an electrostatic potential proximate the riffle members . this special construction includes a layer of an air - pervious polymeric foam disposed intermediate a pair of cloth fabric layers having progressively tighter weave patterns .