Placer mineral concentrator and process

Apparatus for extracting heavy metal from a precious metal-bearing ore comprising:

• a rotatably mounted cylindrical drum having a substantially horizontally disposed axis, said drum having an input end, an output end, and an internal peripheral surface, said input end being substantially closed about input pipe means adapted for flowing a slurry of precious metal ore into said drum at a predetermined rate, the internal peripheral surface of said drum having a plurality of continuously annular riffles of predetermined height evenly spaced from the closed input end to and including the output end and having a plurality of longitudinally extending circumferentially spaced riffles of a height less than said annular riffles, means for selectively rotating said drum at a predetermined speed,
• the size, spacing and respective heights of the longitudinal riffles and annular riffles, and the speed of the rotation of the drum are each such that the slurry is caused to vortex in a helical fashion over the said riffles and build a stream bed-like matrix of heavier particles within compartments formed by the riffles, the speed of rotation of the drum such that the matrix is maintained within the compartment by centrifugal force with the vortex action causing heavier particles to settle and form part of the matrix within the compartments, while the lighter particles are kept in suspension by the vortex action and are carried out of the apparatus through the output end,
• means for selectively and periodically tilting said drum and flushing out said matrix with liquid.