From this site:
Gould Engineering Bazooka Dredge
"The heart of the design, which is patent pending, is the unique
Separator. This new concept separates the precious heavy metals from the much lighter sand and gravel.
The lighter materials are un-effected by the separator and are swept through the device and exit out the aft end.
The heavy materials are greatly effected by the
Separator. The first part of the
Separator has a component, called the
Concentrator, which causes the heavy, (High Specific Gravity), materials, as well as the water, to spin. The heavy materials, due to centrifugal force, are forced against the wall of the inter tube. The
Separator tube, has 22 traps or
slots which allow the heavy material to escape from the inter wall to the
Main Storage Chamber. Once the heavy materials enter this
Storage Chamber, they are trapped until the front end
Nozzle Assembly component is released and the contents poured into a bucket. "
I think he is using the same tech as spinning various specific gravity items in a glass of water