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Experiment with 'Black Sands'


Fsbirdhouse

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Have not seen the topic discussed as such, but am wondering if it isn't possible that black sands that always settle into the same riffles with gold, cannot, to some degree, be made to wash out as do the lighter sands, leaving the riffles cleaner to collect the finer gold?

I am talking about mounting powerful magnets positioned at a point above the riffles just high enough that they do not capture any of the black sands, but low enough to just begin to effect a slight magnetic draw on the sands sufficient to reduce its weight to the point that the flow of water can wash them away as it does the other sands?

I am going to save some black sands out of my next cons to test the theory by putting them on a scale, perhaps on a pedestal above the area where the magnet can draw the scale itself, and then lower a large magnet above the sands until the scale indicates a change in weight without capturing the particals of sand.

Don't know if this is even possible, but if the first few riffles in any sluice can be reserved for gold alone, it could not but help the fine gold recovery, and do so on the cheap.

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The prox of mag would be criticle in order to make the BS levitate/suspend.

I believe there is too tight a tolerance variable for the gap from BS to Mag.

How about a small conveyor type belt running above the first foot or so of the sluice. Inside the belt are stationary magnets that draw the BS to the belt. The BS is carried to either side where the magnets stop and the BS falls away from the belt. :hmmmmm:

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The prox of mag would be criticle in order to make the BS levitate/suspend.

I believe there is too tight a tolerance variable for the gap from BS to Mag.

How about a small conveyor type belt running above the first foot or so of the sluice. Inside the belt are stationary magnets that draw the BS to the belt. The BS is carried to either side where the magnets stop and the BS falls away from the belt. :hmmmmm:

I am sure the prox of magnet is critical, but don't know of anyone who has tested the range that a magnet actually begins to affect the sands.

The range may be greater than we think, with the sand becoming buoyant to some degree, long before we ever see it move, not moving at all before the magnet actually captures it. The moment of 'lift' seeming to be an instantaneous thing.

It is either at rest, or flying away.... in our perception.

It would be fun to see!

BTW: Your idea has merit as well! Anything that's simple, and removes the sand from the system efficiently is the goal.

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The prox of mag would be criticle in order to make the BS levitate/suspend.

I believe there is too tight a tolerance variable for the gap from BS to Mag.

How about a small conveyor type belt running above the first foot or so of the sluice. Inside the belt are stationary magnets that draw the BS to the belt. The BS is carried to either side where the magnets stop and the BS falls away from the belt. :hmmmmm:

This is exactly how we handled it on the big placer mill. There were magnetic rollers at the end of two conveyor runs that drew out the magnetics as the slurry passed over the belts. It got about 1/3 of the volume of magnetic sands out of the way with very little loss of gold. Then there was a section of vibrating box that held the slurry in agitation. We had a roller magnet set within 1" of the bottom of the virating box that got another 1/3 of the magnetic sand with very little loss of gold. The rest was eliminated in cleanup. The magnets were only to remove most of the magnetic sands to provide a longer run time and easier cleanups.

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This is exactly how we handled it on the big placer mill. There were magnetic rollers at the end of two conveyor runs that drew out the magnetics as the slurry passed over the belts. It got about 1/3 of the volume of magnetic sands out of the way with very little loss of gold. Then there was a section of vibrating box that held the slurry in agitation. We had a roller magnet set within 1" of the bottom of the virating box that got another 1/3 of the magnetic sand with very little loss of gold. The rest was eliminated in cleanup. The magnets were only to remove most of the magnetic sands to provide a longer run time and easier cleanups.

No doubt this is the most efficient way in a larger scale operation, but I wonder if something similar could be adapted to any suction dredge, or even a sluice box where no mechanical means would be practical.

As I said above, I have no idea if magnets would do the trick as I outlined, but as I have two large magnets in the garage, I think it's worth a look-see to find out.

Let you guys know how it turns out.

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If you want to get rid of the black sands as you wet wash your material use a LeTrap sluice. I have never seen a sluice do as fine a job of leaving gold and very little other material as it. Properly set up you will be amazed.

You don't need no stinkin magnets.

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If you want to get rid of the black sands as you wet wash your material use a LeTrap sluice. I have never seen a sluice do as fine a job of leaving gold and very little other material as it. Properly set up you will be amazed.

You don't need no stinkin magnets.

But I am getting a leTrap in about a week... in any case.

A dredge will follow, and then we will see about the magnets, unless I find a sluice box as good as LeTrap for the dredge.

Could be!

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I am sure the prox of magnet is critical, but don't know of anyone who has tested the range that a magnet actually begins to affect the sands.

The range may be greater than we think, with the sand becoming buoyant to some degree, long before we ever see it move, not moving at all before the magnet actually captures it. The moment of 'lift' seeming to be an instantaneous thing.

It is either at rest, or flying away.... in our perception.

It would be fun to see!

BTW: Your idea has merit as well! Anything that's simple, and removes the sand from the system efficiently is the goal.

If the distance between the BS particles and the mag remained constant I would think it would work. But, the particles are "suspended" at dif depths in the water.

Amazing what ya can do with a small water wheel. :inocent:

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If the distance between the BS particles and the mag remained constant I would think it would work. But, the particles are "suspended" at dif depths in the water.

Amazing what ya can do with a small water wheel. :inocent:

As they come off the head of the box? They might not be allowed to drop to greatly different depths if kept in suspension (Though surely some would, as all BS particles are not created equal)past the point where they must rise to clear the first riffle in a standard box, or remain at a given level in molded riffles.

Almost too many variables to list as to why it might not work, and if it worked like a charm? Still might not increase the capture of fines enough to mention.

Won't know 'til tried.

Jason G,

If the mag gets 'hairy' then it is capturing the BS particles, and the system would clog in a few moments. This is to be avoided!

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I did it a different way last spring by a new sluice that had a section 2/3rds of the way down it to remove almost all of the black sands and other heavies from beneathe the matting through suction. That slurry went into a hydrofuge to remove the gold that it contained. Ended up being a total waste of time in design and fabrication. It would fill a 5 gallon bucket with almost pure black sand in under 30 minutes to recover a few grains of gold that hadn't got caught in the head box and first few riffles. The cleanup time made it a silly thing to worry about. Fact is that even with riffles loaded with black sands in a sluice with good design you are still going to catch most of the gold as it's still much heavier than the sands and should settle right into it.

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I did it a different way last spring by a new sluice that had a section 2/3rds of the way down it to remove almost all of the black sands and other heavies from beneathe the matting through suction. That slurry went into a hydrofuge to remove the gold that it contained. Ended up being a total waste of time in design and fabrication. It would fill a 5 gallon bucket with almost pure black sand in under 30 minutes to recover a few grains of gold that hadn't got caught in the head box and first few riffles. The cleanup time made it a silly thing to worry about. Fact is that even with riffles loaded with black sands in a sluice with good design you are still going to catch most of the gold as it's still much heavier than the sands and should settle right into it.

I hear this over and over on the one hand, and then I see the dredge fabricators and others talking about three stage sluices to capture the fines.

Sure seems to be a split decision on whether folks are losing fine gold or not.

From all I've read, the LeTrap sluice was a quantum leap in recovery technology, and maybe that should be enough.

But boys will be boys, and if you think you're gonna keep a boy from tinkering with his toys...........'Lotsa Luck'

No pun intended.

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Your idea exists already:

My link

Well, Almost!

I think your idea (Is it yours?) is great. Probably captures the sands nicely, but how often must it be cleaned?

Pretty often, I would think.

I'd like to see magnets utilized in a manner that allows the sands to wash out on their own.

I'm not looking to develop a product for sale, just one I can build and use myself, and if efficient and cheap, post plans on how to make for the DIY crowd.

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