Abstract: A dry placer mining machine and a belt assembly for use therewith. The machine concentrates metallic constituents from a gravel mix by fluidizing the mix with air which passes upwardly through the belt assembly, and moving the fluidized mix over the belt and applying an electrostatic charge thereto. The belt assembly is made up of a composite fabric belt member and a plurality of riffle members which extend transversely across this. The composite fabric belt member is constructed of non-conductive materials so as to minimize dissipation of the electrostatic charge, and this is made up of a finely woven cloth top layer, a reticulated foam middle layer, and a coarse mesh lower layer. The riffle members, in turn, are provided with insulation for preventing the electrostatic charge from being conducted away from the fabric belt member. The belt assembly is driven over the open upper end of a plenum chamber, and air pressure is supplied to this through a blower and ducting.

Abstract: 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.