Can gold be separated from sand with magnets?

[Gold:Au]

The answer is, surprisingly, YES.

A year or two ago I came to the realisation that the magical forces that go on inside of an electric motor could, in theory, be harnessed to separate gold from sand. Now, if I had come up with the idea, surely someone else had done so before and sure enough, William Benson and Thomas Falconer patented a practical methodology of separating non-ferrous metals from non-metals by using magnets. ( patents.google.com/patent/US3448857A )

This technology is used extensively in waste reclamation where it is used to recover metals from chopped up garbage in a fancy machine called an "Eddy Current Separator" that these days use high-speed rotating magnets.

(Note the magnets are spinning inside the head drum, and not attached to it)

So it's a proven existing technology with commercially available hardware that can directly separate gold from dirt, so why don't we see it being used in dry-washers? The fact of the matter is that size matters. The smaller the piece of metal, the less force is exerted upon it so I assume anything smaller than 1mm may not experience enough force to deflect it.

Despite complexity of the concept, it is literally just some spinning magnets, so you can tinker with the concept in your garage. Maybe a vertical column of water may assist cleaning up the fine gold from the black sands?

I would love to see this being useful in mining.

 

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[xracer550]

It only works with magnetic "black" sand the light blond sand will still be mixed with the gold but will be much easier to pan out the cons. Here is the one I made last year .

 

[pepperj]

One of my brokers installed/invented a system to recover precious metals from electronics. The system used air and magnets some attract and some to repel.

 

[Gold:Au]

It only works with magnetic "black" sand the light blond sand will still be mixed with the gold but will be much easier to pan out the cons. Here is the one I made last year .

Not quite - please note the following diagram:

The first roller is your setup - using magnets to pull magnetics (blue) from the dirt.

The cool bit I am talking about is the second roller, where the non-metallics (Yellow) roll over the end of the drum as expected, but the spinning magnets inside the drum launch the non-magnetic metals (Black) off the roller, and onto a separate pile.

I am yet to find a stated reason why it will not work for gold, other than my assumption that the force imparted into the metals is proportional to their size, making it unsuitable for fine gold. At least in the standard dryblower, I would expect it could be incorporated into a fancy counter-flow clean-up process.

 

[Gold:Au]

While we're discussing the magical properties of electricity, now's an ideal time to bring to your attention the existence of electrostatic separators designed especially for gold.

While there's plenty of nerd-level geekery available online to explain the process, it basically boils down to using electrostatic charge to attract fine, dry particles and utilising the fact that electrically conductive particles (such as fine gold) will lose their charge quicker than non-electrically conductive particles (sand, etc) and so detach at a different time.

There appear to be two main types that I can see - the standard roller that uses a similar method to the magnetic separator:




A second, more useful looking style uses electrostatic plates rather than rollers, and this Chinese manufacturer has a very good self-explanatory video:



With prices between $15k and $30k and only 1-2 T/h, it's a specialised bit of kit but again, it is an interesting concept that could be played with in the shed for clean-up.

 

[pepperj]

While we're discussing the magical properties of electricity, now's an ideal time to bring to your attention the existence of electrostatic separators designed especially for gold.

While there's plenty of nerd-level geekery available online to explain the process, it basically boils down to using electrostatic charge to attract fine, dry particles and utilising the fact that electrically conductive particles (such as fine gold) will lose their charge quicker than non-electrically conductive particles (sand, etc) and so detach at a different time.

There appear to be two main types that I can see - the standard roller that uses a similar method to the magnetic separator:




A second, more useful looking style uses electrostatic plates rather than rollers, and this Chinese manufacturer has a very good self-explanatory video:



With prices between $15k and $30k and only 1-2 T/h, it's a specialised bit of kit but again, it is an interesting concept that could be played with in the shed for clean-up.

BUNTING is probably the leader in magnet technology for separation. The unit shown is designed to separate copper chop that has been contaminated with aluminum chop.

Running TECK and BX through the grandulator creates the mixed problem.

I would of loved having a unit as this for separation.

 

[ConceptualizedNetherlandr]

Why do the magnets ( or the field) need to spin?

 

[Gold:Au]

Why do the magnets ( or the field) need to spin?

One of the basic laws of electromagnetism is that when an electrical conductor moves through a magnetic field, (Or a magnetic field field passes over a conductor) an electric current is induced into that conductor. That electric current creates its own magnetic field that interacts with the original magnetic field.

If you design things right, you can harness that electricity by using wires for that conductor and you have a generator.

But if your conductor is just a lump of gold, the electric current creates what are known as "eddy currents" which are just little whirlpools of electricity.

If you were to put a pile of paydirt through an "Eddy current separator", the spinning magnets would create a moving electric field which induces eddy currents into any nuggets of gold, which turns those nuggets into an electromagnet which creates its own magnetic field that repels the original.

If you have strong enough magnets, spinning fast enough, you could literally make those gold nuggets jump.

Impart a little horizontal momentum on them via a conveyor, you could make them jump into a collection bucket.

There are much simpler and cheaper methods of separating nuggets from dirt, but I think the concept is of interest as one of the very few novel separation methods discovered within the last century.

*edit* The magnetic field and the conductor just need to move relative to each other, the faster the better, and spinning the magnets is the easiest way to achieve that.

 

[Oregon Viking]

I use a Cleangold sluice for black sand beach gold. Works great!
Cleangold sluice utilizes magnets as a key part of its design; it incorporates magnetic sheets within the sluice box to attract and trap fine gold particles by attaching them to a layer of magnetite (a magnetic mineral) that is placed on the sluice floor.

 

[ConceptualizedNetherlandr]

One of the basic laws of electromagnetism is that when an electrical conductor moves through a magnetic field, (Or a magnetic field field passes over a conductor) an electric current is induced into that conductor. That electric current creates its own magnetic field that interacts with the original magnetic field.

If you design things right, you can harness that electricity by using wires for that conductor and you have a generator.

But if your conductor is just a lump of gold, the electric current creates what are known as "eddy currents" which are just little whirlpools of electricity.

If you were to put a pile of paydirt through an "Eddy current separator", the spinning magnets would create a moving electric field which induces eddy currents into any nuggets of gold, which turns those nuggets into an electromagnet which creates its own magnetic field that repels the original.

If you have strong enough magnets, spinning fast enough, you could literally make those gold nuggets jump.

Impart a little horizontal momentum on them via a conveyor, you could make them jump into a collection bucket.

There are much simpler and cheaper methods of separating nuggets from dirt, but I think the concept is of interest as one of the very few novel separation methods discovered within the last century.

*edit* The magnetic field and the conductor just need to move relative to each other, the faster the better, and spinning the magnets is the easiest way to achieve that.

The gold is already moving. So why do the magnets need to?

 

[Gold:Au]

The gold is already moving. So why do the magnets need to?

The more magnetic field lines the 'nugget' crosses, the greater the induced force. The commercially available magnets are not strong enough (ie. make enough magnetic field lines) to affect a nugget just passing over the top of it on a conveyor, but placing a dozen or more of them in a drum and rotating them at speed exposes the nugget to probably hundreds (if not thousands) more field lines.

 

[russau]

Sounds good in theory BUT to get a working set up going is PROOF in the pudding . Most people won't get this involved with this type / depth of testing . They will just say I'll get it the next run of material........ OR it's just not worth my time to do all of this . BUT it ALL ADDS UP and you'll capture it in the Winter while you have the time during the cold weather! AIN"T LIFE GRAND !!

 

[Assembler]

Sounds good in theory BUT to get a working set up going is PROOF in the pudding . Most people won't get this involved with this type / depth of testing . They will just say I'll get it the next run of material........ OR it's just not worth my time to do all of this . BUT it ALL ADDS UP and you'll capture it in the Winter while you have the time during the cold weather! AIN"T LIFE GRAND !!

For a test and simple returns on time spent. Why not take PVC pipe drum with magnets that is spinning in a forward direction with two catch bins to see how much separation of materials there is?

Then compare this to both dry and wet sluice box set ups for the returns and time spent?

 

[Assembler]

Since this is posted in the dry washing thread area.
Why not have a spinning PVC magnet drum on the end of a dry washing sluice that is parallels the direction of the sluice box so as to discharge the values to the side of the end or tailings?

My guess is that the speed should be 400 RPM'S or better?
Would a rabbit fur be a good material for the drum wiper unit?
Some simple tests should give some answers.

 

[ConceptualizedNetherlandr]

The more magnetic field lines the 'nugget' crosses, the greater the induced force. The commercially available magnets are not strong enough (ie. make enough magnetic field lines) to affect a nugget just passing over the top of it on a conveyor, but placing a dozen or more of them in a drum and rotating them at speed exposes the nugget to probably hundreds (if not thousands) more field lines.

Each line spending a proportionally shorter time of interaction averaging out to no change in total force. But the force would be variable thus reducing the specificity of the field if it actually does anything to aid separation.

 

[Assembler]

Each line spending a proportionally shorter time of interaction averaging out to no change in total force. But the force would be variable thus reducing the specificity of the field if it actually does anything to aid separation.

The variable effect could take place if the gold / value is attached to other rock?
If there is a electric charge in place perhaps this would effect the effect as well?
There may be other issues as well?

 

[ConceptualizedNetherlandr]

The variable effect could take place if the gold / value is attached to other rock?
If there is a electric charge in place perhaps this would effect the effect as well?
There may be other issues as well?

You might have missed my point. Suppose somehow a magnetic field could be generated in a small space that was somehow strong enough to influence thee path of the falling gold particles regardless of composition.

If the mag field was stationary it would tend to direct materials in ONE way.

But, if the field were moving around creating variability in the force strength and direction the disposition of the trajectory would vary and act against separation causing the destination for the separated particles to become less discrete. Get it?

 

[Gold:Au]

Each line spending a proportionally shorter time of interaction averaging out to no change in total force. But the force would be variable thus reducing the specificity of the field if it actually does anything to aid separation.

The "lines" are like elevation lines on a topographical map, specifying the boundary between two arbitrary values. The closer the lines are together, the greater the rate of change in magnetism the nugget sees which is what imparts the repulsive force.

This is not speculation or spliff enlightenment, this is an extremely well understood electromagnetic interaction, You can even buy an "eddy current separator" today that will separate nuggets from paydirt. (an expensive way of doing it though)

Will it work on specimens? Sure, if it contained enough gold to generate enough force to repel the entire mass.

Will it work on small gold? The number "1mm" seems to be the quoted minimum size in the available commercial units, and I suspect that may be the realistically practical limit for any obvious dry washer design.

That is not to say a small unit couldn't be used to increase the efficiency of a clean-up system using a counterflow water column. (whatever they are called)

This thread was started to bring to forum members' attention a new and potentially useful methodology of separating gold. While the processes work, I make no claims for their practicality or usefulness but hope they may provide the missing key to somebody's project.

 

[Assembler]

You might have missed my point. Suppose somehow a magnetic field could be generated in a small space that was somehow strong enough to influence thee path of the falling gold particles regardless of composition.

If the mag field was stationary it would tend to direct materials in ONE way.

But, if the field were moving around creating variability in the force strength and direction the disposition of the trajectory would vary and act against separation causing the destination for the separated particles to become less discrete. Get it?

Now I may see the point kinda like acting as a riffle to direct materials in one way or direction.