Because these systems use mechanics to help keep or create a suspended medium, we refer to them as “mechanical recovery systems.”

Shaker tables use a finely-tuned vibrating action, with a very mild flow of water, to separate material by weight.

Oscillating sluices create a left and right movement (similar to panning) as material is washed over top by a mild flow of water. Mechanical jigs create a pulsating medium within a chamber that keeps water and material in a state of fluid suspension. There are different ways to create suspended mediums so that gold can be recovered from streambed materials. This is because the slurry is in a liquefied state of suspension, where heavier particles can easily penetrate downward, because gravity is pulling on them much harder than the lighter materials. Since gold is around six times heavier than the average of other materials which make up a streambed, if you pass raw streambed material through the right kind of suspended medium, you are able to drop the gold to the bottom, and direct the lighter materials off the top as tailings.Īs an example of this, if you dropped some gold onto the hard ground, even though the gold is much heavier than the material making up the ground, because the ground is somewhat hard and compacted, it would probably take a very long time for the gold to work its way through to the bottom of the material in that compacted state.īut if you dug up all that ground (and gold), and dumped it into a raging river during a major flood storm, the material would all get churned into a liquid slurry as it is washed downstream in the river, and the gold would very quickly work its way down through to the bottom of the slurry. A suspended medium is a condition of fluidity where materials are allowed to separate because of their relative weights. In gold mining, when we talk about gravity-recovery systems (as opposed to chemical-recovery systems), we are basically talking about the creation of a suspended medium.

How to build a gold dredge