Innovative Gold Recovery Systems for Modern Mining

Free fine gold that has been released from hard rock comes in many forms as it changes its characteristics due to the environment its subjected to after release form the host rock.

Reef gold that has been exposed to natural weathering with the gold being exposed as the rock is weathering away is the most natural type of gold found buy miners as it can be in pieces that can be picked up by hand and washed in a gold dish this can be easily separated and recovered. Most of the gold in the reef formations are microscopic in size and can blow away from the reef with wind and rain then transported by streams into rivers to the sea. The gold that enters a high energy treachery river system can be subjected to abrading buy the rocks and sand traveling in this system making the gold smaller in size and most of the time flat and very thin.

The gold that has travelled in these systems becomes very hard to catch in traditional recovery rifles and matted recovery tables as the gold particles are affected by the flow of water and unable to penetrate the mineral heavies that are contained in these riffles and matts.

This gold is then subject to size, area, weight ratio problems for recovery. All fine gold deposits are different as each deposit has its own origin and release history ie: It can be released by moving ice and frozen gravels carving the host rock away, a river system can cut through the reef the has large flood events that carry big rocks and pound and abrade the reef releasing large nuggets of gold that then can travel many miles all the time being abraded producing more fine gold.

I my experience the amount of fine gold in ratio to heavy gold that you can pick up by hand by weight would easily exceed 100 to 1. The fine gold I have been working with has a peak in the size graph at around 120 microns in size with a thickness of about 5 to 10 microns. This fine gold if placed in clear still water 1 meter deep takes 10 minutes to fully settle to the bottom of a container demonstrating that no table or riffle system can recover the type of gold in a commercial recovery operation.

This recovery technology has been mainly used on black sand heavy mineral deposits with high concentrations of Garnett. Zircon. These conditions have proved very changeling with fluidisation of these materials difficult for the recovery of the gold. This program took many years of work resulting in many thousands of oz’s of gold recovered with many plant changes to present the ore to the recovery concentrators in away that makes recovery possible.

It was found the even though the concentrators would recover the gold you needed the complete recovery plant to make the system work in a way that no dirty water left the circuit without being subjected to the concentrators.

The Pfahlert gold recovery concentrators are not an add on piece of equipment as they require a water balance tank system to maintain the correct feed density ratio to the concentrators to maintain uniform recovery.

The balance tank settling system lets material settle after screen sizing to allow water to be reused in the primary washing circuit as to reduce the amount of water required over all in the washing circuit.

Fresh clean water is added to the rear section of each screening operation to remove any material left by the front screening section. This amount of water matches the outgoing water from the concentrators that was required to put concentrate into the concentrators with a sand pump.

Every fine gold deposit will present its own unique set of problems either primary washing and screening with tropical clays or limited clean water available.

On site evaluation of an indicated fine gold reserve combined with trail mining the next stage producing real results in saleable gold from the operation this reduces the risk in proceeding to a fully committed mining operation.

fine gold in an alluvial gold deposit is far more uniform in distribution than typical medium to heavy alluvial gold recovered by gravity recovery on riffle tables. This very fine gold makes predictable grade control possible.